When vertical mounting rails offer unthreaded (untapped) "clearance holes", EIA specs expect these to be 9/32 inches in diameter (or 0. 1374mm), plus/minus a tolerance of 0. AudioRax Rack Rail Pair, Cut-To-Order | 1/2U Spacing EIA-310 Standard The EIA-310 standard has served as the foundation for 19-inch equipment racks for over five decades. These measurements define how devices are positioned vertically and horizontally within the rack structure. The channel of the rack shall be capable of mounting NetRunnerTM or PatchRunnerTM 2. The cabinet or rack must be one of the following rack types: Standard 19” four-post EIA cabinet or rack, with mounting rails that conform to English universal hole spacing per section 1 of ANSI/EIA-310-D-1992.