SINGLE BULK PACK WD AV-25 2.5-inch SATA hard drives are specially engineered to offer cool quiet operation while providing maximum reliability in 24x7 always-on environments. With support for up to five simultaneous HD video streams, these drives are perfect for DVRs, set-top boxes and digital video surveillance. 500GB, SATA, 3Gb/s, 16MB Cache, 5400RPM, 2.5" Hard Drive.