Sans Digital RAID Enclosures(MR4UT) Drive: SATA 150 & 300 External I/O: USB 2.0 and eSATA 3.5" Drive Bays: 4 x Hot-Swappable Power Supply: 180W (90V to 256V) Form Factor: Cube HDD Trays: 4 Hot-Swappable 3.5" Maximum Capacity: 12TB total storage capacity Cooling Fan: 3.5" Ball Bearing