We don't really see much point in the existence of 2.5-inch drive enclosures, since the drives in that size that aren't part of a PC, or whatever else, usually have a portable, USB-connected design anyway, but Century Japan decided to release such a case regardless of that fact.
The item is called Greenline 2.5-inch (CGL25U3S6G) and supports both SATA HDDs and SSDs of up to 6 Gbps.
The link to the PC is, predictably enough, enabled by the USB 3.0 SuperSpeed interface, but Centruy tossed in a special asset too: UASP.
Short for USB-attached SCSI protocol, it leads to data rates even better than what USB 3.0 normally allows for. Unfortunately, we have no read and write speed numbers to provide, so we can only take Century's word
for it on that.
The Greenline 2.5-inch enclosure weighs 67 grams when empty and will ship later this month (September 2012), for $38 / 30 Euro.