# O vs 理业

The clearest difference is iOS requirement: 理业 at 11.0 against O's 16.0. On price, rating, ratings volume and update cadence there is nothing between them.

Both are free to download. Neither carries in-app purchases, so what you see is what you pay.

On the App Store both sit at effectively the same score — 5.0 for O against 5.0 for 理业. Both are backed by a comparable volume of ratings — 1 and 1 respectively.

O ships an update every 11 months, 理业 every 12 months. The most recent releases landed on September 26, 2026 and September 8, 2026 respectively.

## The numbers

| Metric | O | 理业 |
| --- | --- | --- |
| Price | Free | Free |
| Rating | [5.0 (1 ratings)](https://appshunter.io/ios/app/o-ring-master/id1072051820/reviews) | [5.0 (1 ratings)](https://appshunter.io/ios/app/id1474947206/reviews) |
| Number of ratings | 1 | 1 |
| Positive reviews | 100.0% of reviews | — |
| In-app purchases | No | No |
| Ads | No | No |
| Update frequency | **Every 11 months** | Every 12 months |
| Monetization | Free | — |
| Size | 47 MB | 2 MB |
| Requires iOS | 16.0 | **11.0** |
| Devices | iPhone | **iPhone, iPod** |
| Age rating | 4+ | 4+ |
| Developer | [GE MAO RUBBER INDUSTRIAL CO., LTD.](https://appshunter.io/developer/1078558543) | [Lishui Inverse Enzyme Technology Co., Ltd.](https://appshunter.io/developer/1474947175) |

## 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


### 理业

[App page](https://appshunter.io/ios/app/id1474947206)

**In-app purchases:** none


## Frequently asked questions

### Is O free?

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

### Is 理业 free?

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

### Which has better reviews, O or 理业?

O and 理业 are both rated 5.0 out of 5 on the App Store, from 1 and 1 ratings respectively.

### Do O or 理业 have ads?

Neither O nor 理业 shows ads.

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

O ships an update every 11 months, and 理业 every 12 months. Most recently, O was updated on September 26, 2026 and 理业 on September 8, 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.*