The 2.5" and 3.5" Hard Disk Drive Tray for SS-Tower NAS Servers from QNAP can be used for installing a hard drive into a NAS storage server. These trays are compatible with the SS-439 Pro and 839-Pro QNAP servers and include the necessary hardware for installation. Applied Models: TVS-882ST2, TS-453S Pro (SS-453 Pro), TS-853S Pro (SS-853 Pro), SS-439 and SS-839 series