This device is a direct replacement for a couple of not-so-old Hard Disk Docking Stations, which both didn't always work properly, and in both units I had to buy replacement power supplies.
This unit is extremely well constructed from aluminium. Undo four screws at the rear and remove the internal frame. You can then very easily insert one or two SATA hard disks, fasten them securely with the supplied screws, re-insert the frame and the four screws, and plug it into your PC. And you have a solid, fan cooled, hard disk enclosure that should last forever! Well, a good number of years anyway!