The 155 mm self-propelled gun Mk F3, or the Canon de 155 mm Mle F3 Automoteur (Cn-155-F3-Am), was developed in the early 1950s by the French Army to replace their American M41 Gorilla 155mm self-propelled guns. The Mk F3 is the smallest and lightest 155 mm motorized gun carriage ever produced, and because of its size and low cost it has found considerable success on the export market. Constructed on a modified AMX-13 light tank chassis, the Mk F3 is novel in incorporating room inside for only two of the eight required crewmen (the others riding in support vehicles). This allows the 155 mm gun to be placed on a smaller chassis than that employed by other armies, but exposes the outside crew members to arms fire.