I bought this caddy in order to install a SSD in my Asus Vivo VM42 mini PC. This is the perfect solution because it has the same form factor as the standard 3.5" HDD that originally comes in the PC and allows the new SSD drive to simply plug in to the chassis via the caddy connector. Mounting hardware is provided with the caddy and its outer frame accepts the same coarse thread screws that standard HDDs use while the inner frame uses M3 fine thread screws for the SSD. This is a plus in my application because I reused the coarse threaded screw-on mounting grommets that were on the OEM drive. Then, I installed the caddy (with the SSD mounted) in the same fashion as the original drive for a perfect and secure fit. The only reason that I give it four stars instead of five is because compared to a brand name caddy, this one is a little on the cheap as far as construction and finish are concerned. However, I had originally bought a Rosewill caddy for this project and it doesn't accept the coarse-threaded screws on the outer frame. Instead it takes M3 fine thread screws. In other applications that may be fine, but for me I really needed the coarse threaded holes instead. It was made better though. Oh well, as I said, it worked great and I'm very happy with this find.

I'm upgrading my review now that I've used it for a bit. It is actually a pretty good product. Works perfectly with my Samsung SSD, and fits perfectly in any 3.5" slot.

However, it should have come with screws! I had to spend another $7 on a computer screw kit just to be able to install it.

These rule. They're cheap, small, and strong. They aren't pretty, and they aren't fancy. They require tools. But the work perfectly, and allow you to fit twice as many SSDs in the same number of bays.

PRO:
-half height 3.5" size means you can fit twice as many disks in the same number of bays. Alternatively, if you space them the same as 3.5" drives, you'll be able to move twice the volume of air between them, for better overall system cooling.
-perfect fit for SATA / SAS backplanes.
-all hardware included. You just need a Phillips #2 or #3 screwdriver. JIS drivers should work too.

CON (just some nitpicks, nothing major):
-unfinished steel. I would have preferred painted or plated, but it's fine.
-some edges aren't perfectly clean, and a few were slightly bent. It doesn't matter much in practice, and this adapter won't really be seen once it is installed.
-Regarding SAS Support (this is for servers, it probably doesn't matter for most customers): Supports only single-port SAS. If you use dual-port drives, you'll lose access to the second port.

I purchased this General 2.5" SSD to 3.5" SATA Hard Disk Drive HDD Adapter CADDY TRAY CAGE Hot Swap Plug to allow my SD drive to work in the hot swap bays of a levono sever. The build quality is excellent, strong metal with well build internal connectors. The device worked as advertised to allow my 2.5 SSD to work in a hot swap 3.5" harddrive bay. Would buy again if needed.

I was beginning to wonder if something like this actually existed or if I should invent it and make my millions.

It's common practice for us to purchase workstations and put SSDs in them. I had been searching for this for a while as we oftentimes recommend Lenovo ThinkCentre M73 units to clients and the included 3.5" HDDs are bottom-mounted with four screws. This is probably the fifth different 2.5" to 3.5" mounting bracket we'd tried that actually bottom mounted properly and was low profile enough to fit in the configuration. If you're looking for a solid 2.5" to 3.5" enclosure kit with the standard four bottom mount screws, look no further.

It also comes with twice as many screws as you need, which is a nice thing over time as you install them.