Introduction
Choosing the right Shopify apps can feel like navigating a complex ecosystem. Each tool promises to enhance the customer journey and boost sales, yet the sheer volume of options can lead to decision paralysis. When it comes to wishlists—a crucial feature for capturing customer intent and reducing cart abandonment—merchants often seek solutions that balance functionality, ease of use, and cost. Understanding the nuances between specialized apps is essential for making an informed choice that truly supports growth objectives.
Short answer: Wishlist Hero presents a more robust, feature-rich, and scalable solution with stronger social proof compared to Wishlister, which is simpler and offers basic functionality. Merchants prioritizing advanced marketing integrations, performance tracking, and multi-currency support will likely find Wishlist Hero more aligned with their needs, while those seeking a very basic, low-cost option might consider Wishlister. However, relying on single-purpose apps often introduces operational overhead, making a holistic view of the tech stack important for long-term value.
This analysis provides a feature-by-feature comparison of Wishlister and Wishlist Hero, two prominent Shopify apps designed to add wishlist functionality. The goal is to offer a detailed, objective perspective, helping merchants identify which app best suits their specific operational context and strategic goals, while also considering the broader implications of their app choices.
Wishlister vs. Wishlist Hero: At a Glance
Selecting a wishlist app involves more than just checking off features; it requires aligning the tool with a store's specific operational scale, marketing strategy, and budget. The following table provides a quick overview, highlighting key distinctions between Wishlister and Wishlist Hero to facilitate an initial assessment.
| Aspect | Wishlister | Wishlist Hero |
|---|---|---|
| Core Use Case | Basic wish list creation and management for customer convenience. | Advanced wish list functionality with a focus on conversion via reminders and marketing integrations. |
| Best For | Small stores or merchants needing a very simple, low-cost wish list solution with minimal advanced features. | Growing to large stores seeking to leverage wish lists for proactive marketing, conversion, and multi-region support. |
| Review Count & Rating | 2 reviews, 2.5 rating | 359 reviews, 4.7 rating |
| Notable Strengths | Category-based organization, simple setup, secure user login for saved lists, budget-friendly. | Guest wish list, low stock/price drop email reminders, multi-currency/language, deep marketing pixel integration, robust API support. |
| Potential Limitations | Limited reviews and lower rating suggest potential issues or lack of adoption; basic feature set lacks advanced marketing tools. | Higher pricing tiers for full functionality; potential feature overkill for very small, basic needs. |
| Typical Setup Complexity | Low | Low (automated for popular themes, with free setup help for others) |
Deep Dive Comparison
A closer examination of Wishlister and Wishlist Hero reveals distinct approaches to providing wishlist functionality, each with implications for different types of Shopify merchants. Understanding these differences across various criteria is key to selecting the most appropriate tool.
Core Features and Workflows
Wishlist functionality, at its core, allows customers to save products they are interested in for future purchase. However, the depth and breadth of features built around this core concept vary significantly between apps.
Wishlister: Simplicity in Design
Wishlister focuses on a straightforward approach, providing the essential capabilities for customers to create and manage wish lists. Its primary features include:
- Category-based Wishlists: This allows customers to organize their favorite products into different categories, which can be useful for planning purchases across various product types or occasions. For instance, a customer might create separate lists for "Birthday Gifts," "Home Decor," or "Future Tech Upgrades."
- Social Sharing: Customers can share their wish lists with friends and family via social links. This feature leverages peer-to-peer influence, potentially expanding reach and driving new traffic to the store.
- Secure User Login: Wishlists are saved for future access, requiring user login. This ensures persistence across sessions and devices, enhancing the personalized shopping experience for returning customers.
- Seamless Integration: The app is designed to integrate smoothly with any Shopify store, aiming for a consistent aesthetic and minimal setup friction.
The workflow is simple: customers add items, organize them, and can return to their saved lists. This basic set of features caters to stores where the primary goal is to offer a convenient way for customers to save items without engaging in complex marketing automation.
Wishlist Hero: Advanced Engagement and Conversion Focus
Wishlist Hero extends the basic wishlist concept significantly, integrating features aimed at converting interest into sales through proactive engagement and detailed tracking. Its comprehensive feature set includes:
- Guest Wishlist Functionality: Unlike Wishlister, Wishlist Hero allows users to utilize the wishlist without requiring a login. This reduces friction for new or casual shoppers, broadening accessibility.
- Proactive Email Reminders: A standout feature is the ability to send automated email reminders when a wishlisted product has low stock or experiences a price drop. This directly addresses common purchase triggers, prompting action from interested buyers.
- Multi-Currency and Multi-Language Support: For international merchants, this is a critical capability, ensuring a localized experience for a global customer base. The app adapts to different market needs, which is crucial for maximizing conversion rates in diverse regions.
- Deep Marketing Pixel Integration: Wishlist Hero offers robust integration with popular marketing platforms like Klaviyo, Facebook Pixel, GA4, and TikTok Pixel. This enables merchants to track wishlist activities, retarget users with personalized ads, and analyze the impact of wishlists on conversion through detailed reporting.
- Wishlist Addition from Anywhere: Customers can add items to their wishlists directly from product pages, collection pages, and quick views, streamlining the saving process regardless of where they encounter a product on the site.
- API Support: The availability of REST API and JavaScript API indicates greater flexibility for custom integrations and advanced developers, allowing for bespoke solutions and deeper synchronization with other platforms or internal systems.
- Share Wishlists: Similar to Wishlister, it supports sharing via email and social media (e.g., Facebook), but its integration capabilities suggest a more refined approach to leveraging these interactions for conversion.
Wishlist Hero’s features build a complete ecosystem around wishlists, not just for customer convenience, but as a strategic tool for retention and sales growth. The emphasis on reminders, tracking, and multi-channel integration makes it a more powerful instrument for active marketing.
Customization and Control
The ability to tailor a wishlist app's appearance and behavior to match a store's brand and operational needs is crucial for a consistent customer experience.
Wishlister: Basic Theme Integration
Wishlister emphasizes "seamless integration with any Shopify store," which generally implies that the app's styling will adapt to the store's existing theme with minimal intervention. For merchants who prefer a hands-off approach and are content with the default presentation, this level of integration is sufficient. The descriptions do not specify extensive options for customizing the wishlist button, page layouts, or notifications beyond basic theme adherence. This simplicity means less control over intricate design elements, but also less work for the merchant in terms of setup and ongoing maintenance.
Wishlist Hero: Enhanced Branding and Theming
Wishlist Hero offers a more detailed approach to customization. Its "one-click setup, seamless integration with your theme & ensured using free help" suggests a commitment to visual consistency. Critically, the Silver plan includes "Custom brand" capabilities, indicating that merchants can modify the appearance of the wishlist elements to align perfectly with their brand guidelines. This level of control is valuable for maintaining a cohesive brand identity across the entire shopping journey. The app's ability to work on product, collection, and quick views also implies that the wishlist functionality can be consistently present and styled across various parts of the storefront, contributing to a unified user experience. For advanced users or specific integration needs, the JS API and REST API also provide a foundation for highly customized implementations, allowing developers to extend or modify the app's behavior as required.
Pricing Structure and Value for Money
The cost of an app is always a significant factor, but it must be weighed against the value it provides in terms of features, scalability, and impact on revenue.
Wishlister: Straightforward and Budget-Friendly
Wishlister offers a single, simple pricing plan:
- Basic Plan: $2.99 / month. This straightforward pricing makes Wishlister one of the most budget-friendly options available for basic wishlist functionality. There are no tiers to navigate, which simplifies the decision-making process for merchants. This plan covers the core features of category-based wishlists, sharing, and secure user login. For stores with very tight budgets or those that only require the most fundamental wishlist features, this low monthly cost represents a clear value proposition. However, merchants should consider if this basic feature set will meet their long-term growth and marketing objectives. This app offers a pricing structure that scales as order volume grows, though its single plan means scaling is through external tools.
Wishlist Hero: Tiered for Scalability and Features
Wishlist Hero employs a tiered pricing model, designed to cater to different sizes of businesses and feature requirements, including a free option:
- Free Plan: Provides code-free setup, up to 500 wishlist additions/month, wishlist sharing, detailed reports, and multi-currency/language support. This is an excellent starting point for new or very small stores, allowing them to implement wishlist functionality without an upfront cost and begin assessing app-store ratings as a trust signal without financial commitment.
- Silver Plan: $4 / month. Includes everything in the Free plan, increases to 1,000 wishlist additions/month, adds custom branding, Klaviyo, GA4, FB & TikTok pixel integration, low stock and on-sale email reminders, and JS API. This tier offers significant value, unlocking key marketing and customization features at a modest price increase.
- Gold Plus Plan: $17 / month. Builds on Silver, offering up to 5,000 wishlist additions/month, and adds integrations with SendGrid, Klaviyo & OmniSend, along with REST API access. This plan is suited for growing businesses that require deeper email marketing automation and greater API flexibility.
- Platinum Plan: $29 / month. Encompasses all Gold Plus features, scaling up to 10,000 wishlist additions/month. For even higher volumes, merchants are prompted to contact the developer. This tier is designed for larger, high-volume stores with extensive wishlist activity.
Wishlist Hero’s tiered approach means merchants pay for what they need, with options to scale as their business grows. The presence of a free plan and progressive feature unlocks across tiers allows for better comparing plan fit against retention goals and a clearer view of total retention-stack costs as business needs evolve. This model offers greater flexibility and long-term value, especially for merchants leveraging wishlists for active marketing campaigns.
Integrations and “Works With” Fit
An app’s ability to integrate with other tools in a merchant’s tech stack is vital for a seamless workflow and to avoid data silos.
Wishlister: Generic Compatibility
Wishlister's description states it "seamlessly integrates with any Shopify store." This generally indicates a basic level of compatibility with the Shopify platform itself, rather than specific integrations with third-party applications. It implies that the app is built using standard Shopify APIs and theme structures, making it functional across different themes without requiring complex custom coding. However, for merchants looking to connect their wishlist data with email marketing platforms, analytics tools, or other customer engagement apps, Wishlister's capabilities in this area are not specified in the provided data. This means merchants might need to develop custom solutions or accept a more fragmented approach to data management.
Wishlist Hero: Robust Ecosystem Integrations
Wishlist Hero excels in its explicit and extensive list of integrations, making it a stronger choice for stores operating with a more complex and interconnected tech stack. It "works with" a variety of popular Shopify ecosystem apps and marketing platforms:
- Quick View Apps: Boost Commerce Quick View, Buddha, qikify. This ensures that customers can add items to their wishlist even from quick view pop-ups, improving the user experience and capturing intent at multiple touchpoints.
- Search Apps: Secomapp Searchanise, Globo. Integration with search tools means wishlist functionality is consistent even within advanced search results or filters.
- Email Marketing & CRM: Klaviyo, Omnisend, Mailchimp, Sendgrid. These integrations are critical for leveraging wishlist data in email campaigns, such as sending reminders for low stock or price drops, or segmenting audiences based on wishlisted items. The Gold Plus plan specifically mentions SendGrid, Klaviyo & OmniSend integration, highlighting deeper connectivity.
- Analytics & Advertising: Klaviyo, GA4, FB Pixel, TikTok Pixel. These integrations enable comprehensive tracking of wishlist activities, allowing merchants to understand customer behavior, measure the impact of wishlists on conversions, and build highly targeted retargeting campaigns across various advertising channels. This level of data integration offers substantial strategic advantages.
The breadth of integrations for Wishlist Hero means that wishlist data can be centrally managed and acted upon across various marketing and operational tools, providing a more holistic view of customer engagement and a stronger foundation for a data-driven strategy. Merchants can verify these integrations by checking merchant feedback and app-store performance signals on the app listing.
Analytics and Reporting
Understanding how customers interact with wishlists and the subsequent impact on sales is crucial for optimizing strategies.
Wishlister: Limited Insights (Not Specified)
The provided description for Wishlister does not specify any built-in analytics or reporting capabilities. While the app allows for customer login to save wishlists, there is no mention of tracking wishlist additions, popular wishlisted items, or the conversion rate of wishlisted products. This suggests that merchants using Wishlister would need to rely on general Shopify analytics or third-party tools to infer the impact of their wishlist feature, which may involve manual data extraction and analysis. The absence of direct reporting limits the ability to gain actionable insights specific to wishlist performance.
Wishlist Hero: Detailed Tracking and Reporting
Wishlist Hero places a strong emphasis on data and analytics. Even its Free plan includes "Detailed Reports," providing merchants with foundational insights into wishlist activity. As merchants upgrade to higher tiers, the integration capabilities expand significantly:
- Activity Tracking: The app explicitly states it can "Track products, customers and their activities." This provides granular data on which products are most popular, who is adding items to wishlists, and how these activities relate to their broader customer journey.
- Pixel Integrations: The Silver plan unlocks integrations with Klaviyo, GA4, FB Pixel, and TikTok Pixel. These are not just for advertising, but for comprehensive data collection. GA4 integration allows for advanced event tracking and reporting within Google Analytics, enabling merchants to analyze wishlist engagement alongside other website interactions. Facebook and TikTok pixels facilitate audience building and performance measurement for social media campaigns targeting wishlist users.
- Conversion Impact: By feeding data into these analytics and marketing platforms, merchants can directly measure the impact of wishlists on conversion rates, average order value, and customer lifetime value. This allows for data-driven optimization of marketing efforts and demonstrates a clearer return on investment for the wishlist feature.
Wishlist Hero’s robust analytics and tracking features provide merchants with the necessary tools to understand and optimize their wishlist strategy, making it a powerful asset for data-conscious businesses. Merchants looking for an integrated approach to data collection and reporting will find this particularly valuable when confirming the install path used by Shopify merchants.
Customer Support Expectations and Reliability Cues
The quality of customer support and the overall reliability of an app are paramount for minimizing operational disruptions and ensuring a smooth user experience.
Wishlister: Limited Data, Potential Concerns
With only 2 reviews and an average rating of 2.5, Wishlister provides very limited social proof regarding its reliability and customer support. A low number of reviews, especially coupled with a lower average rating, can raise concerns for potential users. It might indicate:
- Limited Adoption: The app may not have a large user base, which can sometimes lead to slower development cycles or less community support.
- Unaddressed Issues: The low rating, even from a small sample size, could point to unresolved bugs, integration challenges, or a lack of responsiveness from the developer.
- Unclear Support Channels: The description does not mention specific support channels (e.g., email, chat, phone), making it difficult to set expectations for assistance.
For merchants considering Wishlister, this lack of extensive positive feedback means there's less public information to gauge the developer's commitment to ongoing support and product improvement.
Wishlist Hero: Strong Social Proof and Dedicated Support
Wishlist Hero, in contrast, boasts 359 reviews with an impressive average rating of 4.7. This substantial volume of positive feedback is a strong indicator of:
- Widespread Adoption and Trust: A high number of reviews suggests a large and satisfied user base, implying the app is robust and widely trusted within the Shopify ecosystem.
- Reliable Performance: A high rating typically reflects consistent performance, effective functionality, and minimal issues encountered by users.
- Proactive Customer Care: The description explicitly highlights "Fast and responsive customer care" and offers "free help" for theme installation. This commitment to support, backed by hundreds of positive reviews, instills confidence that assistance is readily available when needed.
- Developer Engagement: Apps with high review counts and ratings often signify an engaged developer who actively updates the app, addresses user feedback, and provides ongoing support.
For merchants, Wishlist Hero's strong social proof and explicit mention of dedicated support services translate into higher confidence in the app's reliability and the developer's ability to assist with any issues or integration needs. Merchants looking into reviewing the Shopify App Store listing merchants install from will find the extensive positive feedback a compelling trust signal.
Performance, Compatibility, and Operational Overhead
The technical aspects of an app, including its impact on store speed, compatibility with different environments, and the overall maintenance burden, are critical for long-term operational efficiency.
Wishlister: Basic and Minimalist Approach
Wishlister's description focuses on its "seamless integration with any Shopify store," which generally implies a lean and non-intrusive design. A minimalist app with basic functionality tends to have less code to load, potentially resulting in a lower impact on page load times. This is often an advantage for smaller stores or those prioritizing extreme simplicity and speed above advanced features.
However, the lack of detailed technical specifications or explicit performance claims means merchants rely on the implied simplicity. Without specific mentions of mobile responsiveness, compatibility with various Shopify themes or versions, or internal optimization for speed, merchants must assume a standard level of performance. Operational overhead for Wishlister is likely low due given its single, simple plan, which means less time spent on evaluating feature coverage across plans. The maintenance burden would typically be minimal due to the limited feature set, though the developer's responsiveness to updates or issues remains less clear given the low review count.
Wishlist Hero: Optimized for Modern Commerce
Wishlist Hero explicitly addresses several performance and compatibility concerns, positioning itself as a robust solution for contemporary e-commerce. Key aspects include:
- Performance: Described as "Fast and responsive," indicating developer awareness and optimization for speed. This is crucial as page load times directly impact user experience and SEO.
- Automated Installation & Support: "Automated install for popular Shopify themes (and help to install for other themes)" reduces compatibility headaches. This proactive support ensures that the app functions correctly across a wide range of store designs, minimizing the need for merchant-side troubleshooting.
- Broad Compatibility: It "Works on product, collection and quick views," demonstrating compatibility with common display elements across the storefront. This ensures a consistent user experience regardless of where a customer interacts with products.
- GDPR Compliance: Explicit mention of GDPR compliance is vital for merchants operating in regions with strict data privacy regulations, reducing legal and operational risks associated with data handling.
- API Support (REST & JavaScript): The availability of APIs provides extensive flexibility for developers to integrate Wishlist Hero into complex environments, customize its behavior, or ensure compatibility with highly specialized themes or headless Shopify setups. This is particularly valuable for Shopify Plus merchants or those with advanced development needs.
Wishlist Hero’s focus on responsiveness, broad compatibility, and adherence to regulatory standards suggests a higher level of operational maturity. While its richer feature set might imply a slightly higher operational overhead in terms of configuration for its advanced integrations, the benefits of comprehensive tracking and proactive customer engagement often outweigh this. The app's transparent approach to compatibility and performance considerations offers more confidence for merchants seeking a scalable and reliable wishlist solution. When planning retention spend without app sprawl surprises, merchants will find Wishlist Hero's features to be more thoroughly developed.
The Alternative: Solving App Fatigue with an All-in-One Platform
While specialized apps like Wishlister and Wishlist Hero offer targeted solutions for specific needs, many Shopify merchants eventually encounter "app fatigue." This phenomenon arises from the proliferation of single-function tools, each designed to address a different aspect of customer engagement—loyalty, reviews, wishlists, referrals, and more. The result is a fragmented tech stack characterized by tool sprawl, which can lead to several challenges. These include fragmented data across disparate systems, inconsistent customer experiences due to varying app interfaces, increased integration overhead, and a cumulative rise in subscription costs. Managing multiple apps also consumes valuable time that could be better spent on strategic growth initiatives.
An alternative approach that has gained significant traction is the adoption of all-in-one retention platforms. These integrated solutions combine multiple essential customer engagement features into a single system, streamlining operations and providing a unified view of customer data. Growave embodies this "More Growth, Less Stack" philosophy, offering a comprehensive suite designed to enhance customer lifetime value through interconnected modules. If consolidating tools is a priority, start by choosing a plan built for long-term value. This integrated approach not only simplifies app management but also fosters a more cohesive and impactful customer retention strategy, allowing merchants to focus on outcomes rather than tool logistics.
Growave's platform provides a robust solution for merchants looking to mitigate the challenges of app fatigue. Instead of juggling separate apps for loyalty, reviews, wishlists, and referrals, merchants can manage all these critical functions from one dashboard. This centralized control ensures that customer data is unified, leading to more accurate segmentation and personalized engagement strategies. For instance, the platform’s loyalty points and rewards designed to lift repeat purchases can be seamlessly integrated with its review collection features, allowing customers to earn rewards for submitting valuable feedback. This synergy across modules helps in creating a consistent and rewarding customer journey that incentivizes repeat purchases and fosters brand advocacy.
The benefits extend beyond just consolidation. With Growave, merchants gain access to a powerful set of tools that work in harmony to elevate customer engagement. The ability to collect and showcase collecting and showcasing authentic customer reviews directly influences conversion rates, while integrated loyalty programs reduce reliance on constant discounting by offering meaningful incentives. Additionally, merchants can learn from real examples from brands improving retention by effectively combining these features. This integrated ecosystem means a customer's journey, from wishlisting an item to making a purchase, earning loyalty points, and leaving a review, is all tracked and managed within a single system. This level of interconnectedness enhances the customer experience, making interactions feel more cohesive and intentional.
By integrating critical customer engagement functionalities, Growave helps merchants reduce the total cost of ownership associated with a multitude of single-purpose apps. This includes not just subscription fees but also the hidden costs of managing multiple vendor relationships, ensuring integrations work correctly, and resolving compatibility issues. An all-in-one platform fosters efficiency, allowing teams to collaborate more effectively and leverage insights from a single, reliable data source. This strategy empowers businesses to implement retention programs that reduce reliance on discounts and build sustainable growth. The unified platform also ensures a consistent user experience on the storefront, as all engagement widgets share a common design language and backend infrastructure. For merchants aiming to build trust and drive conversions, social proof that supports conversion and AOV is vital, and a platform that integrates reviews with other retention tools creates a stronger impact. Ultimately, embracing a solution like Growave allows merchants to simplify their tech stack, gain a clearer view of total retention-stack costs, and accelerate sustainable growth by focusing on a holistic customer journey. Exploring customer stories that show how teams reduce app sprawl provides practical insights into this approach. For merchants scaling rapidly, selecting plans that reduce stacked tooling costs becomes a strategic priority.
Conclusion
For merchants choosing between Wishlister and Wishlist Hero, the decision comes down to the desired level of functionality, marketing sophistication, and budget. Wishlister presents a minimalist, budget-friendly option for stores requiring only the most basic wishlist creation and sharing capabilities. Its simplicity appeals to those prioritizing low cost and a straightforward user experience without complex marketing integrations. However, its very limited social proof and basic feature set may not suffice for evolving business needs.
Wishlist Hero, conversely, offers a robust and feature-rich solution built for active marketing and conversion optimization. With proactive email reminders, deep pixel integrations, multi-currency support, and strong social proof from numerous positive reviews, it stands out as a more complete tool for growing businesses aiming to leverage wishlists strategically. Its tiered pricing model also offers scalability, from a free plan for startups to more comprehensive options for high-volume stores. While its advanced features come with higher costs at the upper tiers, the value proposition is strong for merchants focused on data-driven growth.
Ultimately, neither app is a universal "winner," as the best choice depends on a merchant's specific context. Wishlister suits new or very small stores with fundamental needs and a minimal budget. Wishlist Hero is better positioned for growing to large businesses that need to actively engage customers, track performance, and integrate wishlist data with their broader marketing ecosystem. However, for merchants seeking to avoid the common pitfalls of app fatigue—fragmented data, inconsistent customer experiences, and escalating costs from a multitude of single-purpose apps—exploring an all-in-one solution like Growave offers a strategic advantage. Such integrated platforms provide a holistic approach to customer retention, unifying loyalty, reviews, referrals, and wishlists under one roof, thereby improving efficiency and delivering a cohesive customer journey. By mapping costs to retention outcomes over time, businesses can make more informed decisions about their tech investments. To reduce app fatigue and run retention from one place, start by reviewing the Shopify App Store listing merchants install from.
FAQ
How do wishlists benefit an e-commerce store?
Wishlists serve multiple purposes, including reducing cart abandonment by allowing customers to save items for later, capturing customer intent even if they are not ready to purchase immediately, and providing valuable data on product popularity. They can also facilitate gift planning and social sharing, expanding a store’s reach and driving repeat purchases by reminding customers of items they desire.
What are the key differences between a basic and an advanced wishlist app?
A basic wishlist app typically allows customers to save products and perhaps share them. An advanced app expands on this with features like guest wishlists, automated email reminders (e.g., for price drops or low stock), multi-currency support, deep integrations with marketing and analytics platforms (e.g., Klaviyo, GA4, Facebook Pixel), and API access for custom development. Advanced apps focus on leveraging wishlist data for proactive marketing and conversion.
When should a merchant consider an all-in-one platform instead of specialized apps?
Merchants should consider an all-in-one platform when they experience "app fatigue," which includes managing multiple subscriptions, dealing with fragmented customer data across different tools, struggling with integration complexities, or noticing inconsistent customer experiences. An integrated platform offers a centralized solution for loyalty, reviews, wishlists, and referrals, streamlining operations, consolidating data, and often providing better value for money by reducing total operational overhead and fostering a cohesive customer journey.
Can wishlist apps integrate with email marketing platforms?
Yes, many advanced wishlist apps offer direct integrations with popular email marketing platforms like Klaviyo, Omnisend, and Mailchimp. These integrations allow merchants to leverage wishlist data for targeted email campaigns, such as sending reminders about saved items, announcing price drops or low stock, or personalized product recommendations, significantly enhancing conversion potential.








