WD 5TB My Passport — a compact 2.5" USB 3.0 portable hard drive that runs off bus power alone, no separate power brick needed. 5400rpm platter with a 128mb cache, USB 3.0 interface (USB 2.0 backward compatible so it still works with an older port, just at USB 2.0 speed), in a 111x82x19mm pocketable black enclosure. A straightforward external backup/overflow-storage drive for a laptop or desktop.