These are 2 external HDD’s - the first one (WDXML600UE) is a 2.5" 5400 rpm box with capacities ranging from 40 to 80 GByte. Its bigger brother, the WDXF3200JB, carries 3.5" disks with capacities from 120 to 320 GByte.IT also has 8 MByte of cache and spins its platters at 7200 rpm. It comes with a USB 2.0 and FireWire connector and you also get a 8 in 1 card reader that allows you to copy the contents of your cards to the harddrive without using a PC.