The BT tanks were lightly armoured but produced in large numbers to provide support for the infantry - over 5,000 BT-7 were produced. The Christie suspension chassis was imported from the USA in 1931 and this design was to continue through all BT variants. This BT-7 was developed in 1937 by fitting a 76.2mm L-10 gun in a new turret with a secondary DT machine gun. The tank had a crew of 3 and carried 60 rounds of ammunition.