The W84 is a two stage radiation implosion warhead with a variable yield ranging from 0.2 kiloton up to 150 kilotons. The W84 was designed at Lawrence Livermore National Laboratory starting in 1978, based on the B61 nuclear bomb weapon design originated at Los Alamos National Laboratory. Manufacture of this warhead commenced in 1983. Sources differ regarding the total number of units produced, though the figure is known to be either 350 or 530.