It is a 1 tb western digital my book av pvr expander. Connects through eSATA to the back of your pvr. Allows you to expand the recording space of your pvr. Has a power button in the back. When you plug it in to a pvr you can reformat it to your system. Comes with power cord and eSATA cable. In great working condition. Selling for 50 dollars. If interested please message me. Thanks.