RTII425SMR5 RAID Tower II (black color) with 1 4X1 eSATA/USB 2.0 Hardware Port Multiplier installed. Install up to four 2.5" SATA hard drives or SSD of any capacity. Drives are added or removed like tape cartridge from each drive bay with no special tool required. Connect to system via USB 2.0 or eSATA port (connecting cables included). Drives can be configured as FAST2 (2 drive RAID 0 Striping), SAFE2 (2 drives RAID1 Mirroring), BIG 2 (2 drives Concatenation), 3 drives in RAID 3, or 3 drives in RAID 5. RAID setting via a rotary switch on the back. OS independent, can be used on any system. See product detail at http://www.addonics.com/products/raid_tower/raid_tower_stii.asp