American National Standard for Dimensions and Centering Systems for Projection Lamps - 35 mm Integral Reflector, Rim Reference Lamps with GZ4 Bases
National Electrical Manufacturers Association
Specifies lamp dimensions of 35 mm (1.38 in.) diameter integral reflector rim reference projection lamps with GZ4 bases so that interchangeability with the appropriate holding systems will be ensured.
This product replaced by:ANSI/NEMA C78.357-2010 - For incandescent lamps: Tungsten Halogen Lamps (non-vehicle)