scope:

This Standards publication contains definitions, dimensions , and tolerances for recessed luminaires designed to use fluorescent, high-intensity discharge, and incandescent light sources.

Drawing examples show fluorescent lamps. However, these drawings also apply to high-intensity discharge, compact fluorescent, incandescent, and other lamp sources.

This Standard does not apply to hard metric dimensioned products. However, soft metric dimensions or direct metric conversions may be applied throughout this Standard as one inch equals 25.4 millimeters.