The Sony Microvault USB drive is a fairly standard USB flash drive. It comes in a number of capacities, up to, I believe, 4 GB. The increased capacities come with corresponding price increases. I believe I paid $25 for my 1 GB model.
The 1 GB model, although it's not the largest available, almost has more space than I know what to do with. I have my entire My Pictures and My Documents folders backed up on it, and I'm only using about a third of the drive's capacity.
The unit's size is also a selling point. It is about the same size as other drives, but has a feature I haven't seen in other brands: the ability to retract the USB dongle into the drive's body. This makes the unit small and sleek when being transported, and makes this drive a great buy for the price.