WD WD6003FFBX 6TB Red PRO 3.5" SATA3 NAS Hard Drive, Capacity 6TB, 256MB, Form Factor 3.5", SATA 6GB/s, RPM 7,200. Designed specifically with medium or large scale business customers in mind, WD Red Pro drives are available for up to 24-bay NAS systems. Engineered to handle high-intensity workloads in 24x7 environments.