Use fixed shelves to support equipment without rack-mounted brackets such as modems, CPUs, small power supplies and monitors. Shelves mount to the Universal EIA 5/8”- 5/8”-1/2” (15.9 mm -15.9 mm -12.7 mm) alternating hole pattern of the four vertical mounting rails, and three depths are offered in 18”, 24” and 29” (460 mm, 610 mm and 740 mm). Shelves have adjustable mounting depths of 13” to 24” (330 mm to 610 mm) for the 18” (460 mm) shelf, 17” to 28” (430 mm to 710 mm) for the 24” (610 mm) shelf and 24” to 38” (610 mm to 970 mm) for the 29” (740 mm) shelf.