The Velociraptor is a 2.5 inch drive enclosed in a 3.5 inch mounting frame. You can take it out of the frame and I think it will fit but I'm not sure if the drive is thin enough.

Edit: It's thicker than a standard 2.5 inch drive so you won't be able to close the case as it's too tall.

The Raptor hasn't always been a 2.5" drive. The older Raptors were always 3.5" like my Raptor X drives from 2005.