The MK 1 Illuminating grenade is 4.4 inches in length, 2.1 inches in diameter. The total weight is 9.5 ounces. The fuze delay is 7 seconds. The burning time is 25 seconds with a 50,000 candlepower illuminating compound. It consists of two sheet steel cups joined together by a force fit plastic sleeve. The lower half contains the illuminating compound and a charge of black powder, which, when ignited by the fuze, blows the grenade apart and ignites the pyrotechnic. The upper half contains the fuze assembly.