The Mark 82 (Mk 82) is an unguided, low-drag general-purpose bomb (dumb bomb), part of the U.S. Mark 80 series. With a nominal weight of 500 lb (227 kg), it is the smallest of those bombs in current service, and one of the most common air-dropped weapons in the world. Although the Mk 82's nominal weight is 500 lb (227 kg), its actual weight varies considerably depending on its configuration, from 510 lb (232 kg) to 570 lb (259 kg). It is a streamlined steel casing containing 192 lb (87 kg) of Tritonal high explosive. The Mk 82 is offered with a variety of fin kits, fuses, and retarders for different purposes. There are three modes of delivery available for the Snakeye fin assembly. They are retarded, unretarded, and in-flight selection (pilot option) of either mode. RETARDED MODE.—In the retarded mode of delivery, the fins open to retard or slowdown the weapon. Since the aircraft and the weapon are traveling at the same speed when the weapon is released, the weapon and the aircraft arrive at the target at the same time. During low-level bombing, the aircraft could be damaged; therefore, the retarded mode of delivery is used during low-level bombing. The fin assembly is positively armed in the retarded configuration. In this configuration, the fin release arming wire is looped over a permanent structure on the bomb rack. As the weapon is released from the aircraft, the arming wire is pulled from the fin release band, and the spring-loaded fins pop open. The fins are forced to the full-open position by the air stream, which causes the weapon to rapidly decelerate and allows the releasing aircraft sufficient time to safely clear the target area.