19 inch is the standard size frame to install the various modules of equipment. Each module has a front panel that has a width of 19 inches (482.6 mm), including edges or ears that stand on each side of the equipment, which serves to bind the module to the rack with screws.

Equipment designed to be placed in a Rack Server is usually called rack-mount, rack-mount instrument, a rack mounted system, a rack mount chassis, sub-rack, rack mountable, or occasionally simply shelf only. Altitude electronic equipment module also standardized as multiples of 1.75 inches (44.45 mm) or one rack unit or 1 U rack server has a high standard of 42 U.

Rack servers have different sizes of depth (depth) as a function of the shelf, such as 850 mm and 1,150 mm. Depth adjustable shelves with equipment modules to be installed in the rack.