U is the EIA standard cabinet space unit, 1U = 1.75 inches = 4.45 cm (1 inch = 2.54cm). Manufacturers convention Uunitsused to measure the height of equipment. When the parameters on the router, server, hub, and switch devices are 1U, this means they have a height of 1U. The system of holes on the hanging bars in the cabinet is divided into clusters, each cluster includes 3 square holes of 0.5 inch side. Each of these 3-square-hole systems is designed in parallel to form part of the space inside the cabinet with a height of 1U equivalent to 1.75 inches. Rack-mounted devices are often designed around this U unit. For example, 6U rack cabinets, 10U racks, 15U racks, 20U racks, 27U racks, 42U racks or switches, 1U, 2U routers… Usually, the rack will have 4 standard bars that are mounted in the cabinet for mounting. equipment, The usable distance of the cabinet is the distance from the center of the 2 holes located on 2 equal TC rods and exactly 19 inches. So it is called a standard 19 inch cabinet, used to catch network and telecommunications equipment… standard 19 inch. There is also a standard 23-inch Rack cabinet. The size of the rack is calculated in width (W) x height (H) x depth (D), depending on how many or few devices you can choose, how many U? from the small 6U-9U-10U-15U to the larger one like 20U-27U-32U-36U-42U-45U. With each line of cabinets with the same U unit, there are often many different types of depth: D600, D800 D600. Depending on the depth of your device, will choose the right size, no waste.
Rack-mount equipment manufacturers often manufacture their products based on rack units (U). Because this unit helps determine the number of devices placed in the rack. The distance between groups of 3 punch holes on the rack’s flange is determined from the center of the hole to the other, and the variation of this distance depends on whether the rack is punched square or round. So the unit U means the unit of height, 1U = 1.75 inch = 4.45 cm (1 inch = 2.54cm). The larger the Rack cabinet, the higher the U, the more devices and servers can be placed.