Very nice, lightly used 2-bay 3.5" external hard drive enclosure equipped with two (2) Hitachi Deskstar 2TB 3.5" form-factor SATA HDDs, for a total storage capacity of 4TB. Currently formatted for Windows, but will work with Mac as well if reformatted. Interfaces are USB 2.0, eSATA, and Firewire 400 and Firewire 800.