As noted in the installation guide:
Rack Requirements
This section provides the requirements for the standard open racks.
The rack must be of the following type:
- A standard 19-in. (48.3-cm) wide, four-post EIA rack, with mounting posts that conform to English universal hole spacing, per section 1 of ANSI/EIA-310-D-1992.
- The rack post holes can be square 0.38-inch (9.6 mm), round 0.28-inch (7.1 mm), #12-24 UNC, or #10-32 UNC when you use the supplied slide rails.
- The minimum vertical rack space per server must be two RUs, equal to 3.5 in. (88.9 mm).
Equipment Requirements
The slide rails supplied by Cisco Systems for this server do not require tools for installation if you install them in a rack that has square 0.38-inch (9.6 mm), round 0.28-inch (7.1 mm), or #12-24 UNC threaded holes. The inner rails are pre-attached to the sides of the server.
However, if you install the slide rails in a rack that has #10-32 round holes, a bladed screwdriver is required to remove the larger square/round mounting pegs from the front of the slide rails.
Slide Rail Adjustment Range
The slide rails for this server have an adjustment range of 26 to 36 inches (660 to 914 mm).
