BT (fast tank) series based upon the Christie M1931 tank.
BT-2 had turret with 37mm gun and one MG. BT-2 built in late 1931, it went into full production the following year. BT-5 was the first major production model. Tank had a larger turreet for 45 mm 20K gun, a new M-5 engine and stronger suspension. Next to appear, in 1935, was the BT-7 series. BT-7 had a new turret and welded armor. Tank BT-7 was deployed in considerable numbers and several were captured by Germans and Finns. BT-7M tank had to be virtually redesigned, so as to be able to take the W-2 diesel engine.
Total production: 8059 tanks.