This is the prefect drive sled for installing large capacity 3.5" HDD. Most of them come with "non standard" mounting points now. Which means can't be installed properly without this sled.
For 6TB or below, it's possible to get a standard mount point HDD. But for 8TB or above, I haven't seen one so far. So, this sled is crucial if you want to max out your cMP's storage capacity.
Anyway, it's just a metal sled with the correct mount point. Build with very good quality, Nothing can really go too wrong.
I only give it 4 starts because for this kind of zero technology product, I expect the price can go a little bit lower.