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NEMA ANSI C78.24:2001
Electric lamps - two-inch (51-mm) integral-reflector lamps with front covers and gu5.3 or gx5.3 bases
Sets forth the physical and electrical characteristics of the group of incandescent lamps that have 2 in. (51 mm) integral-reflector lamps with front cover.
NEMA: National Electrical Manufacturers Association [nema]