Mark 3 Fat Man external components AN 219 contact fuze (four) Archie radar antenna Plate with batteries (to detonate charge surrounding nuclear components) X-Unit, a firing set placed near the charge Hinge fixing the two ellipsoidal parts of the bomb Physics package (see details below) Plate with instruments (radars, baroswitches and timers) Barotube collector California Parachute tail assembly (0.20-inch (5.1 mm) aluminium sheet)