# Drillstring Toolbox Premium vs Gas Compressibility Factor Z

The clearest difference is price: Gas Compressibility Factor Z at Free against Drillstring Toolbox Premium's $24.99. Gas Compressibility Factor Z also leads on update cadence (every 8 months vs every 24 months). On ads, in-app purchases, device support and iOS requirement there is nothing between them.

Gas Compressibility Factor Z is free to download; Drillstring Toolbox Premium costs $24.99 up front. Neither carries in-app purchases, so what you see is what you pay.

Drillstring Toolbox Premium ships an update every 24 months, Gas Compressibility Factor Z every 8 months. The most recent releases landed on September 20, 2026 and October 7, 2026 respectively.

## The numbers

| Metric | Drillstring Toolbox Premium | Gas Compressibility Factor Z |
| --- | --- | --- |
| Price | $24.99 | **Free** |
| In-app purchases | No | No |
| Ads | No | No |
| Update frequency | Every 24 months | **Every 8 months** |
| Size | 1 MB | 3 MB |
| Requires iOS | 14.0 | **13.0** |
| Devices | iPhone, iPad, iPod | iPhone, iPad, iPod |
| Age rating | 4+ | 4+ |
| Developer | [Bureau Veritas North America, Inc.](https://appshunter.io/developer/1770295442) | [Carlos Moura](https://appshunter.io/developer/407501202) |

## What reviewers say

### Drillstring Toolbox Premium

[App page](https://appshunter.io/ios/app/drillstring-toolbox-premium/id1222651738)

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

**In-app purchases:** none


### Gas Compressibility Factor Z

[App page](https://appshunter.io/ios/app/gas-compressibility-factor-z/id1626924678)

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

**In-app purchases:** none


## Frequently asked questions

### Is Drillstring Toolbox Premium free?

Drillstring Toolbox Premium costs $24.99, with no in-app purchases.

### Is Gas Compressibility Factor Z free?

Gas Compressibility Factor Z is free to download, with no in-app purchases.

### Do Drillstring Toolbox Premium or Gas Compressibility Factor Z have ads?

Neither Drillstring Toolbox Premium nor Gas Compressibility Factor Z shows ads.

### Which is updated more often, Drillstring Toolbox Premium or Gas Compressibility Factor Z?

Drillstring Toolbox Premium ships an update every 24 months, and Gas Compressibility Factor Z every 8 months. Most recently, Drillstring Toolbox Premium was updated on September 20, 2026 and Gas Compressibility Factor Z on October 7, 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.*