The Mark 16 torpedo was a redesign of the United States Navy standard Mark 14 torpedo to incorporate war-tested improvements for use in unmodified United States fleet submarines. The torpedo was considered the United States standard anti-shipping torpedo for twenty years; although significant numbers of Mark 14 wartime production remained in inventory. This hydrogen peroxide propelled, 21 inch (53 cm) torpedo was 246 inches (6.25 m) long and weighed 2 tons (1800 kg). The Mod 0 warhead contained 1260 lb (572 kg) of TPX explosive and was the most powerful conventional submarine torpedo warhead ever used by any Navy. The United States used TPX explosive which was about 75% more powerful (7405 J/g.) than the Type 97 explosive in the larger Japanese Type 93 Mod 3. (780 kg of Type 97, 4370 J/g.)