Add unlimited storage capacity for storing files, music, photos and movies, with the Western Digital My Book Essential external hard drive. With this easy-to-use drive, all you need to do is to plug it into computer's USB 2.0 port, and you are ready to store any of the files. This 3.5" hard drive features a storage capacity of 250 GB. The 8 MB cache and high RPM of 7200 combine to give an unparalleled performance for data transfers.