The ReadyRails sliding rail kit for 1U Systems, including the PowerEdge R320, R420 and R620 provides tool-less support for racks with square or unthreaded round mounting holes including all generations of Dell racks. They also support tooled mounting in 4-post threaded racks via an optional adapter brackets kit. The optional cable management arm (CMA) can be mounted on either the left or right side of the sliding rails without the use of tools for fast and easy deployment. Alternative Part Numbers: CWJ0X 0CWJ0X 9D83F 09D83F 3PCVD 03PCVD W6M3K 0W6M3K 331-5463 **Does Not Include Cable Management Arm***