1922-3-300-01-U 20 inches depth. The built-in front lip makes sliding the shelf in and out easy, and the 4-point adjustable mounting make this sliding rack shelf a smart addition to any network rack or cabinet. 17. Kendall Howard 1922-3-300-01-U 1U 20 -Inch Rack Mountable Sliding Shelf - EIA compliant - Black Powder Coated Finish 19 inches EIA compliant.