Synology Rail Kits are designed for installing your Rack Station on the rack. The Synology Rail Kit Sliding comes with sliding rails, making it easy to slide the Rack Station in & out for easy maintenance, while the Synology Rail Kit Fixed secures your Rack Station on a rack. Applied models: Synology 2U Rail Kit Sliding: RS3412xs, RS3412 R Pxs, RS3411xs, RS3411 R Pxs, RS2212+, RS2212RP+, RS2211+, RS2211RP+, RX1211, RX1211RP Synology 1U Rail Kit Sliding: RS812+, RS812RP+, RS812, RS810+, RS810RP+, RS411, RS409+, RS409RP+, RS409, RX410, RX4 Synology 1U Rail Kit Fixed: RS812+, RS812RP+, RS812, RS810+, RS810RP+, RS411, RS409+, RS409RP+, RS409, RX410, RX4