This product is either discontinued or we cannot get that from suppliers.
Qnap TS-459U RAIL-C01, 1U RACK, Sliding Rail Kit, Server.
The 1U Rail Kit for 1U Rackmount Models from Qnap is designed for use with 1U Rackmount models, including TS-410U, TS-419U, TS-439U, TS-459U, TS-459U+ and TS-469U.