Unit

Unit — unit of the vertical dimension of the equipment in a standard rack server and communication equipment.
• Equal to 44.45 mm (or 1.75 inches). Mounting holes (e.g., a standard 19-inch rack) for bearing structures are arranged so that when mounted horizontally with no gaps only mounted equipment having a height of an integer number of «units».
• For scheduling of equipment in the racks need to know its height in the «Units». Usually this height is indicated among the main characteristics of the equipment. For example: «rack mount enclosure, 2U».