In 1941, large numbers of T-60s began to appear, reinforced in 1942 with the similar T-70. Both of these light tanks had torsion-bar suspension, light armour, and small engines. Their simple construction kept them in production even though their combat value was limited. The T-60 had only a 20 mm gun while the T-70 had a 45 mm. In addition, both had one-man turrets, making them difficult to crew effectively. The T-70 formed the basis for the later SU-76 self-propelled gun.