The M113 is the ultimate American armored personnel carrier, and it is the most-produced American armored fighting vehicle in history with over 80,000 made. It is essentially an armored box on tracks, and has lent itself to a plethora of specialized designs. The commander was placed behind the engine and was provided with a vision cupola fitted with the .50cal MG. Troop access was through a large rear ramp which also had an entry door in the left side, and a large roof hatch was provided over the passenger compartment. M113 was air-droppable at a weight of 18,600lbs (8,440kg).