EIA – Electronic Industries Association – Racks
The Electronic Industries Association (or EIA) publish standards for the electronics industry. They cover a broad range of equipment and EIA-Wiring and Interconnection Documents.
A standard rack specification is defined in EIA-310 and has been around for many decades. Several important features of 19″ racks are standardized. The Rack Unit (RU or U), horizontal and vertical hole spacing as well as the front panel width and rack opening. Tolerances are also set for each dimension.