Single Bulk Pack - WD AV-GP 4.0TB SATA 6Gb/s Internal 3.5-inch AV Hard Drive, 64MB Cache, IntelliPower. Power-conserving WD AV-GP SATA hard drives with WD GreenPower Technology meet the 24x7 requirements of demanding audio and video environments. They deliver cool and quiet operation and reliability perfect for audio/video applications such as PVRs, DVRs, set-top boxes (STBs), and surveillance video recording.