# O vs Tolerance Master

The clearest difference is in-app purchases: O at none against Tolerance Master's 1. Tolerance Master's advantage is update cadence (every 6 months vs every 11 months). On price, ads, device support and iOS requirement there is nothing between them.

Both are free to download. Tolerance Master sells 1 in-app purchase, starting at $0.99 per month. O asks for nothing beyond the download.

O ships an update every 11 months, Tolerance Master every 6 months. The most recent releases landed on November 2, 2026 and October 31, 2026 respectively.

## The numbers

| Metric | O | Tolerance Master |
| --- | --- | --- |
| Price | Free | Free |
| Rating | **[5.0 (1 ratings)](https://appshunter.io/ios/app/o-ring-master/id1072051820/reviews)** | — |
| Number of ratings | **1** | — |
| Positive reviews | 100.0% of reviews | — |
| In-app purchases | **No** | Yes |
| Ads | No | No |
| Update frequency | Every 11 months | **Every 6 months** |
| Monetization | Free | — |
| Size | 47 MB | 3 MB |
| Requires iOS | **16.0** | 17.0 |
| Devices | iPhone | **iPhone, iPad** |
| Age rating | 4+ | 4+ |
| Developer | [GE MAO RUBBER INDUSTRIAL CO., LTD.](https://appshunter.io/developer/1078558543) | [磊 高](https://appshunter.io/developer/1879509033) |

## What reviewers say

### O

[App page](https://appshunter.io/ios/app/o-ring-master/id1072051820)

This app provides a comprehensive offline tool for selecting standard rubber seal sizes, including O-Rings, X-Rings, and Back-Up Rings. It offers dimension searches, housing calculations for various sealing applications, and supports multiple international standards in both metric and imperial units.

**Highlights:** Offline standard rubber seal size selection, Search for O-Ring, X-Ring, and Back-Up Ring sizes, O-Ring housing calculations for sealing applications, Supports multiple international standards (AS568, METRIC, JIS, etc.), Metric and Imperial unit support, Substitutable O-Ring size suggestions

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

**In-app purchases:** none


### Tolerance Master

[App page](https://appshunter.io/ios/app/tolerance-master/id6759722609)

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

**In-app purchases (1)**

| Purchase | Price | Billing |
| --- | --- | --- |
| Pro Version | $0.99 | per month |


## Frequently asked questions

### Is O free?

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

### Is Tolerance Master free?

Tolerance Master is free to download, with in-app purchases available.

### Do O or Tolerance Master have ads?

Neither O nor Tolerance Master shows ads.

### Which is updated more often, O or Tolerance Master?

O ships an update every 11 months, and Tolerance Master every 6 months. Most recently, O was updated on November 2, 2026 and Tolerance Master on October 31, 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.*