Connect Two Removable SATA Hard Drives through a Single USB 3.0 Connection. The SAT3520U3R USB 3.0 to Dual 3.5-inch SATA Trayless Hard Drive Enclosure makes adding fast external storage easy, by turning any two 3.5-inch internal SATA hard drives into an external hard drive. Large capacity drives (tested with up to 4TB per bay) can be used to greatly enhance your computer''s storage/backup capabilities. The hard drive enclosure features a trayless system that eliminates having to mount and fasten the hard drive into the enclosure or tray, for quick and easy installation or removal.Using the SuperSpeed USB 3.0 interface, which is up to 10 times faster than the previous USB 2.0, makes backing up and transferring large files faster than ever, while still being usable on older USB 2.0 systems. With built-in RAID capabilities (0, 1, BIG, JBOD), the two drives can be combined for speed, redundancy or capacity or even left as separate drives, based on situation needs.