Original Item: The US nomenclature is SIGNAL, ILLUMINATION, AIRCRAFT AN M41 DOUBLE STAR. The signal consists of one red star and one green star in a heavy fiberboard case with a brass case head. The signal colors are indicated by the closing wad, half red and half green. The fiberboard and brass construction was used early in World War Two and was replaced by the all-aluminum case of the later War years. Original 37-mm flare cartridges are EXTREMELY RARE and the early versions are virtually unobtainable.

US-issue 37-mm flare cartridges are compatible with British-issue 1½-inch flare pistols.