# Trimix Tools vs The O2ptimaCM Checklist

The clearest difference is in-app purchases: Trimix Tools at none against The O2ptimaCM Checklist's 4. Trimix Tools also leads on price ($6.99 vs $9.99) and ratings volume (5 vs 1). On rating, update cadence, ads and monetization model there is nothing between them.

Trimix Tools costs $6.99 and The O2ptimaCM Checklist $9.99 up front. The O2ptimaCM Checklist sells 4 one-off in-app purchases. Trimix Tools asks for nothing beyond the download.

On the App Store both sit at effectively the same score — 5.0 for Trimix Tools against 5.0 for The O2ptimaCM Checklist. That said, the two scores are not equally well evidenced: Trimix Tools has 5 ratings behind it against 1, so its average is the more settled of the two.

Both ship on a similar rhythm, roughly every 4 months. The most recent releases landed on November 10, 2026 and November 12, 2026 respectively.

## The numbers

| Metric | Trimix Tools | The O2ptimaCM Checklist |
| --- | --- | --- |
| Price | **$6.99** | $9.99 |
| Rating | [5.0 (5 ratings)](https://appshunter.io/ios/app/trimix-tools/id289220808/reviews) | [5.0 (1 ratings)](https://appshunter.io/ios/app/the-o2ptimacm-checklist/id6469104578/reviews) |
| Number of ratings | **5** | 1 |
| Positive reviews | 100.0% of reviews | — |
| In-app purchases | **No** | Yes |
| Ads | No | No |
| Update frequency | Every 4 months | Every 4 months |
| Monetization | Paid | Paid |
| Size | 6 MB | 2 MB |
| Requires iOS | **15.6** | 17.0 |
| Devices | **iPhone, iPad, iPod, Mac** | iPhone, iPad |
| Age rating | 4+ | +4 |
| Developer | [Greg Mclaughlin](https://appshunter.io/developer/284919983) | [Andrew Austin](https://appshunter.io/developer/1708589155) |

## What reviewers say

### Trimix Tools

[App page](https://appshunter.io/ios/app/trimix-tools/id289220808)

This app provides essential tools for divers to plan and blend Trimix gases. It calculates optimal mixes based on depth, oxygen partial pressure, and equivalent narcotic depth, and supports various cylinder filling scenarios. Calculations are available offline and can be customized with saved settings.

**Highlights:** Trimix blending and planning, Depth and partial pressure calculations, Equivalent Narcotic Depth (END) calculation, Saltwater and freshwater support, Cylinder filling and bleed down calculations, Metric and Imperial system support, Offline functionality, Saved settings and custom mixes

**Features:** Vision Pro support

**In-app purchases:** none


### The O2ptimaCM Checklist

[App page](https://appshunter.io/ios/app/the-o2ptimacm-checklist/id6469104578)

This app provides digital checklists for rebreather assembly, helping divers manage their build process. It includes countdown timers for critical breathing stages and a summary view with caution alerts for missed steps. Transition from paper to a digital format for efficient and environmentally friendly diving preparation.

**Highlights:** Digital rebreather assembly checklists, Countdown timers for breathing stages, Summary view of build progress, Caution blocks for missed steps, Paperless dive preparation

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

**In-app purchases (4)**

| Purchase | Price | Billing |
| --- | --- | --- |
| Tiny Tip | $0.99 | one-time |
| Small Tip | $1.99 | one-time |
| Medium Tip | $4.99 | one-time |
| Large Tip | $9.99 | one-time |


## Frequently asked questions

### Is Trimix Tools free?

Trimix Tools costs $6.99, with no in-app purchases.

### Is The O2ptimaCM Checklist free?

The O2ptimaCM Checklist costs $9.99, and also offers in-app purchases.

### Which has better reviews, Trimix Tools or The O2ptimaCM Checklist?

Trimix Tools and The O2ptimaCM Checklist are both rated 5.0 out of 5 on the App Store, from 5 and 1 ratings respectively.

### Do Trimix Tools or The O2ptimaCM Checklist have ads?

Neither Trimix Tools nor The O2ptimaCM Checklist shows ads.

### Which is updated more often, Trimix Tools or The O2ptimaCM Checklist?

Trimix Tools ships an update every 4 months, and The O2ptimaCM Checklist every 4 months. Most recently, Trimix Tools was updated on November 10, 2026 and The O2ptimaCM Checklist on November 12, 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.*