# O vs Sound Meter Plus

The clearest difference is price: O at Free against Sound Meter Plus's $2.99. O also leads on update cadence (every 11 months vs every 39 months). Sound Meter Plus's advantage is device support (3 vs 1) and iOS requirement (12.0 vs 16.0). On ads and in-app purchases there is nothing between them.

O is free to download; Sound Meter Plus costs $2.99 up front. Neither carries in-app purchases, so what you see is what you pay.

O ships an update every 11 months, Sound Meter Plus every 39 months. The most recent releases landed on October 12, 2026 and October 11, 2026 respectively.

## The numbers

| Metric | O | Sound Meter Plus |
| --- | --- | --- |
| Price | **Free** | $2.99 |
| 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 | No |
| Ads | No | No |
| Update frequency | **Every 11 months** | Every 39 months |
| Monetization | Free | — |
| Size | 47 MB | 10 MB |
| Requires iOS | 16.0 | **12.0** |
| Devices | iPhone | **iPhone, iPad, iPod** |
| Age rating | 4+ | 4+ |
| Developer | [GE MAO RUBBER INDUSTRIAL CO., LTD.](https://appshunter.io/developer/1078558543) | [Heng Jia Liang](https://appshunter.io/developer/1532000635) |

## 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


### Sound Meter Plus

[App page](https://appshunter.io/ios/app/sound-meter-plus/id1612179628)

**Features:** macOS Compatibility

**In-app purchases:** none


## Frequently asked questions

### Is O free?

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

### Is Sound Meter Plus free?

Sound Meter Plus costs $2.99, with no in-app purchases.

### Do O or Sound Meter Plus have ads?

Neither O nor Sound Meter Plus shows ads.

### Which is updated more often, O or Sound Meter Plus?

O ships an update every 11 months, and Sound Meter Plus every 39 months. Most recently, O was updated on October 12, 2026 and Sound Meter Plus on October 11, 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.*