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.