A rocket-propelled grenade (RPG) is a shoulder-fired, anti-tank weapon system which fires rockets equipped with an explosive warhead. These warheads are affixed to a rocket motor and stabilized in flight with fins. Some types of RPG are reloadable while others are single-use. RPGs, with the exception of self-contained versions, are loaded from the Muzzle. RPGs are very effective against armored vehicles such as armored personnel carriers (APCs).