The original AK was also known as the AK-47. It was a gas-operated, selective-fire weapon. Like all 7.62-mm Kalashnikov assault rifles, it fired the Soviet 7.62 x 39-mm M1943 round and used a standard 30-round curved box magazine. The AK came in two versions: one with a fixed wooden stock, and another, the AKS, with a folding metal stock issued primarily to parachutist and armor troops. Except for the differences in the stock and the lack of a tool kit with the AKS, the two version were identical. The early AK's had no bayonet, but the version with the fixed wooden stock later mounted a detachable knife bayonet.