The 19-inch standard has a modular structure and ensures that components can be seamlessly incorporated. The entire width behind the mounting flanges (incl. screws) should amount to a maximum of 449 mm. The width of the subrack opening is divided by the divider unit, 1 HP = 5.08 mm (2/10"). The entire height of the subrack is described using a multiple of a height unit, 1 U = 44.45 mm (13/4").