O vs Tolerance Master
Price, ratings, monetisation and update history for both apps, side by side — with what reviewers say about each.
O
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.
- 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
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GMORS O-Ring Master is the completed tool for standard rubber seal sizes. When you use this APP, you don't need to have internet and catalog. Except O-Ring sizes, it also includes the search functions of X-Ring and Back-Up Ring. Otherwise, you can also use O-Ring Housing to choose suitable O-Ring in your application. Main functions are as follows: Dimension Search:O-Ring, X-Ring and Back-Up Ring. - MM and Inch are both available. - Full standard O-Ring series: AS568, BS 4518, GB/T 3452.1, JIS B2401 P, JIS B2401 G, JIS B2401 S, JIS B2401 V, SMS 1586 and METRIC. - Collocated Back-Up for AS-568 O-Ring. - Substitutable O-Ring sizes within tolerance are available. O-Ring Housing: Piston Sealing、Rod Sealing and Face Sealing. - MM and Inch are both available. - Support calculation for both Static and Dynamic sealing applications (Face sealing is with static calculation only). - Up to 7 O-Ring standards ( AS568, METRIC, JIS B2401 P/G/S/V, JASO F404, GB/T 3452.1, BS 4518 and SMS 1586) for most of size requirement of different groove design.
Tolerance Master
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Tolerance Master is a limits-and-fits workspace for mechanical design, machining, inspection, and education. Based on the ISO 286 and GB/T 1800 tolerance systems, it connects direct lookup, inverse fit selection, visual checking, and saved results in one focused workflow. LIMITS & FITS • Basic sizes greater than 0 and up to 3150 mm • Common hole zones A–ZC and shaft zones a–zc • Valid tolerance grades filtered dynamically by size and tabulated availability • Upper and lower deviations plus maximum and minimum limit sizes • Minimum and maximum clearance with clearance, transition, or interference classification • Switch results between micrometres and millimetres SOLVE FROM THE TARGET • Enter the clearance or interference range you need • Rank standard H-basis combinations deterministically • Compare candidates and return one to the main calculator for verification • Start quickly from preferred fit combinations VISUAL AND TRACEABLE • See the zero line, hole and shaft tolerance zones, and clearance range together • Save up to 100 calculations locally and restore them in one tap • Share a structured text summary of inputs, deviations, limits, and fit type • Move between Calculator, Fit Guide, and History workspaces Standards data and calculations run on device. Engineering inputs and saved history are not uploaded. This app is an engineering aid and does not reproduce the standards. Before critical design or production release, verify the applicable standard edition, drawing requirements, material, process, and inspection method. This app includes a 3-day local trial. Continued Pro access requires a separate monthly subscription purchase. A purchased subscription renews automatically unless cancelled in your Apple account settings. Terms of Use (EULA): https://www.apple.com/legal/internet-services/itunes/dev/stdeula/
Screenshots
Verdict
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.
Scored on Price · Rating · Positive reviews · Number of ratings · Update frequency · Ads · In-app purchases · Monetization · Best chart rank · Devices · Requires iOS
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.
| Parameter | O | Tolerance Master |
|---|---|---|
| Price | Free | Free |
| Rating | 5.0 (1 ratings) — better | — |
| Positive reviews | 100.0% of reviews | — |
| Number of ratings | 1 — better | — |
| Update frequency | Every 11 months | Every 6 months — better |
| Ads | No | No |
| In-app purchases | No — better | Yes |
| Monetization | Free | — |
| Devices | iPhone | iPhone, iPad — better |
| Requires iOS | 16.0 — better | 17.0 |
| Further details — not scored | ||
| Size | 47 MB | 3 MB |
| Age rating | 4+ | 4+ |
| Developer | GE MAO RUBBER INDUSTRIAL CO., LTD. | 磊 高 |
In-app purchases
O
No in-app purchases
Tolerance Master
- Pro Version$0.991 Month









