In keeping with Raptor tradition, WD's VelociRaptor breaks new performance ground for SATA drives by combining a 3GB/s SATA interface with a 10K-RPM rotational speed. That makes it a nice option for servers, among other things, and WD decided to enhance that proposition by making the VelociRaptor a 2.5" drive. The drive then adapts to 3.5" drive bays by snapping into a combination drive sled/heat sink/paper weight, if needed.
Trouble is, the power and SATA I/O connectors remain on the back of the 2.5" drive (scroll to the bottom here for a look), completely out of place for a 3.5" hot-swap enclosure to a SAS/SATA backplane. Tragicomic, one would have to say.
WD saw the dramedy and decided to act. Behold, today they've announced a new version of the VelociRaptor intended to be compatible with 3.5" backplane enclosures. The new drive appears to nestle into a redesigned drive sled that includes extenders for the power and SATA connectors, as you can see in the picture on the right (Source: WD).
WD says these new drives are now shipping. No word on whether the person responsible for the original VelociRaptor drive sled was summarily executed, despite persistent rumors.