# Klein Borescope ET21 vs Supreme One

The clearest difference is update cadence: Supreme One at every 3 days against Klein Borescope ET21's every 2 months. Klein Borescope ET21's advantage is iOS requirement (12.0 vs 15.1). On price, ads, in-app purchases and device support there is nothing between them.

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

Klein Borescope ET21 ships an update every 2 months, Supreme One every 3 days. The most recent releases landed on October 4, 2026 and September 18, 2026 respectively.

## The numbers

| Metric | Klein Borescope ET21 | Supreme One |
| --- | --- | --- |
| Price | Free | Free |
| In-app purchases | No | No |
| Ads | No | No |
| Update frequency | Every 2 months | **Every 3 days** |
| Size | 19 MB | 58 MB |
| Requires iOS | **12.0** | 15.1 |
| Devices | iPhone, iPod | **iPhone, iPad, iPod** |
| Age rating | 4+ | 4+ |
| Developer | [Klein Tools](https://appshunter.io/developer/440692921) | [Stratus Data Systems, Inc.](https://appshunter.io/developer/467745017) |

## What reviewers say

### Klein Borescope ET21

[App page](https://appshunter.io/ios/app/klein-borescope-et21/id6740300461)

**Features:** macOS Compatibility

**In-app purchases:** none


### Supreme One

[App page](https://appshunter.io/ios/app/supreme-one/id6751670708)

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

**In-app purchases:** none


## Frequently asked questions

### Is Klein Borescope ET21 free?

Klein Borescope ET21 is free to download, with no in-app purchases.

### Is Supreme One free?

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

### Do Klein Borescope ET21 or Supreme One have ads?

Neither Klein Borescope ET21 nor Supreme One shows ads.

### Which is updated more often, Klein Borescope ET21 or Supreme One?

Klein Borescope ET21 ships an update every 2 months, and Supreme One every 3 days. Most recently, Klein Borescope ET21 was updated on October 4, 2026 and Supreme One on September 18, 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.*