# O vs ISO

The clearest difference is price: O at Free against ISO's $0.99. O also leads on update cadence (every 3 months vs every 18 months) and iOS requirement (12.1 vs 15.6). On ads, in-app purchases and device support there is nothing between them.

O is free to download; ISO costs $0.99 up front. Neither carries in-app purchases, so what you see is what you pay.

O ships an update every 3 months, ISO every 18 months. The most recent releases landed on October 12, 2026 and September 28, 2026 respectively.

## The numbers

| Metric | O | ISO |
| --- | --- | --- |
| Price | **Free** | $0.99 |
| Rating | **[3.8 (5 ratings)](https://appshunter.io/ios/app/o-ring/id485346224/reviews)** | — |
| Number of ratings | **5** | — |
| Positive reviews | 83.3% of reviews | — |
| In-app purchases | No | No |
| Ads | No | No |
| Update frequency | **Every 3 months** | Every 18 months |
| Monetization | Free | — |
| Size | 26 MB | 1 MB |
| Requires iOS | **12.1** | 15.6 |
| Devices | iPhone, iPad, iPod | iPhone, iPad, iPod |
| Age rating | 12+ | 17+ |
| Developer | [Trelleborg Sealing Solutions](https://appshunter.io/developer/396863758) | [Bjarne Berge](https://appshunter.io/developer/1209858941) |

## What reviewers say

### O

[App page](https://appshunter.io/ios/app/o-ring/id485346224)

This app helps users calculate O-Ring dimensions and find compatible materials for their applications. It provides recommendations based on ISO standards and supports both metric and inch measurements.

**Highlights:** O-Ring housing calculation, O-Ring size recommendations by ISO standard, Quick search by national/international standards, O-Ring tolerance calculation, Metric and inch unit switching, Chemical compatibility check, Integration of Trelleborg Sealing Solutions Videos

**Features:** macOS Compatibility

**In-app purchases:** none


### ISO

[App page](https://appshunter.io/ios/app/iso-5167/id1356345079)

**Features:** macOS Compatibility, Vision Pro support

**In-app purchases:** none


## Frequently asked questions

### Is O free?

O is free to download, with no in-app purchases.

### Is ISO free?

ISO costs $0.99, with no in-app purchases.

### Do O or ISO have ads?

Neither O nor ISO shows ads.

### Which is updated more often, O or ISO?

O ships an update every 3 months, and ISO every 18 months. Most recently, O was updated on October 12, 2026 and ISO on September 28, 2026.

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*Compared by [AppsHunter](https://appshunter.io/) from daily US App Store data. Review summaries are generated from verbatim App Store reviews.*