SINGLE BULK PACK WD Black WD3200BEKX 320 GB SATA 6 Gb/s 16 MB cache 7200 RPM 2.5-inch internal 9.5 mm hard drive. WD Black hard drives are designed for enthusiasts and creative professionals looking for leading-edge performance. These 2.5-inch mobile drives are perfect for high-performance applications like photo and video editing gaming and power PCs.