QNAP REXP-1220U-RP 12-Bay 2U Rackmount Expansion Unit - Host Interface: Three SAS 12Gbps 4x Wide Port, Drive Interface: 16x 3.5 inch SAS/SATA 12/6Gb/s, SAS/SATA 3Gb/s Hard Drive or 2.5 inch SAS/SATA SSD Bays, 3 x 6 cm Smart Cooling Fans, For use with TS-x70U-RP, RS-x79U-RP, TS-ECxx80U-RP, RS-x71U-RP Series Enclosures, 2U Rackmountable, Hard Drives Not Included