Unlike in the classic Doom and Doom II, the BFG 9000 in Doom 3 no longer uses the same ammo as the Plasma gun, but its own type of cell instead. The BFG Cell exists as a green cylinder with an actively vibrating sphere inside (similar to an atom), and holds 4 charges. Unlike in Doom II, BFG cells are very hard to come by and are placed in relatively obscure locations, and it is therefore recommended to use the weapon sparingly.