The CoolMax HD-360-U2 External Hard Drive Enclosure is a fanless USB 2.0 external enclosure that supports PATA 3.5" hard drives. PATA is synonymous with EIDE, UATA, Parallel ATA, and Ultra ATA. Any of those drives will work in this enclosure. SATA drives will NOT work with this. Don't try using an adapter either, because it'll just make the back of the enclosure hang out.
The drive is mounted in a bay, very similar to installing it inside your computer. Some enclosures don't require you do put it in a bay, but this one does. This is probably better for stability and heat, but it also adds to the time it takes if you wish to switch out multiple drives rapidly. This enclosure is fanless, meaning that it keeps a low temperature just by contact between the drive and the body, which is made of aluminum to help dissipate the heat. An AC adapter is provided as well -- USB alone would not generate enough power to spin up the hard drive inside.
Blue and green LEDs on the front indicate when the drive is switched on as well as when it is being accessed. The external design is quite slick, all black with silver streaks. If this provides too much contrast with your setup (say, if you use a Mac), try a different enclosure.
Overall, I like this enclosure. I bought it because it was the cheapest at the time and I had a gift certificate for the site. All enclosures are pretty much the same, they only vary in price and design, so find one you're happy with in terms of how it looks, make sure it's not too expensive, and go for it!