3 cm) (two- or 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). For more information, see Requirements Specific to Perforated Cabinets. 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. It defines the. Learn about server rack spacing, including rack units, mounting hole patterns, rack width, and depth, to improve equipment installation, airflow management, and rack organization.