The Western Digital WD6400AAKS-22A7B2 640GB Caviar Blue 3.5" Hard Drive is a reliable internal desktop drive designed for use with both PC and Mac computers. With a storage capacity of 640GB and a rotation speed of 7200 RPM, this hard drive offers fast read speeds of up to 3 Gbps and transfer rates of 550 Mbps. It features a SATA III interface and is shock-resistant, making it a durable and efficient choice for storing large amounts of data. The drive is part of the Caviar Blue product line by Western Digital and has a cache size of 16MB, providing ample storage space for various computing needs.