FSボックス 多機能モジュールツールキット(FSモジュール & DAC/AOCケーブル用、赤色)

First of all: it does exactly what it says on the product page, and 'what it says on the product page' is very useful. I can't fault it for that, so it gets 5 stars.

That being said though, I do feel like there is room for improvement on the software side.

1. The "Free" FS box checkbox is slightly misleading. While the terms don't hide the fact that it's free only in very specific circumstances (namely, buying over $10,000 in transcievers), it's worth reiterating that you'll probably be paying $200-300 for the "Free" FS box. I feel like a better phrasing of this would be a "Trial" FS box. So if you get an FS box, make sure you'll actually get use from it.
2. The FS box is cloud connected, and as a general rule of thumb, I consider that to be an anti-feature. This is no exception. If I buy a FS box, then I would expect it to work even if FS.com goes out of business and its servers shut down. This is not the case, and is something to be aware of.
3. There is no native linux app, and the native windows one doesn't work in bottles.

And some nit picks:

4. The mobile UI could be improved. It's too cluttered, and it's not easy to find the FS box utility. It's something you easily get used to, though.
5. If the web version requires Chrome anyway, it only makes sense to use the WebUSB/WebSerial/WebBluetooth APIs to connect to the FS box. This allows it to be extraordinarily cross platform and avoids the requirement of running a background service.

But overall, it's a really smooth experience that's not really possible with any other manufacturer that I've come across. Kudos to the FS.com team!

The FS Box is a valuable, and necessary tool for any network engineer. We were having various networking issues and once we received the box, we were able to successfully diagnose multiple issues and correct them, resulting in a very stable network. The FS box is highly recommended for use in any networking environment. We’re looking forward to continual use to support our mission critical environment.

Very nice and simple tool for changing modules fw.
Really, it takes some seconds totally.
It just clearing differencies between of vendors.