T-26 A, T-26 Model 1931: First produced between 1931 and 1933. It was very close to the Vickers Type A.
T-26A-1: First British tank to arrive in Russia and was designated this.
T-26A-2, T-26A-3, T-26A-4, T-26A-5: Twin turret.
T-26A1: There was a water cooled MG in each turret.
T-26A2: There was an air cooled MG in each turret.
T-26A5: Two turrets with a long 37 mm in the right turret and an air cooled MG in the left turret.
T-26V: Main commander's version of A-4 or A-5. Originally had left turret removed. There was a frame aerial on the hull.
OT-26: (Ognemetnig Tank "flamethrower tank") Flame-thrower placed in right-hand turret with left-hand turret being removed. Based on T-26A. Some later models kept main gun. The oil tanks and compressed air bottles were in the hull on the left. It could fire about 70 1-second bursts up to 25 / 35 meters. Approximately 500 were built from 1933 on.
ST-26: (Saperskiy Tank "engineer tank") Bridge carrying version converted from the 1931 model T-26. Carried a seven meter wheel channel bridge and its weight limit was 14 tons. Another version was intended to be driven into a ditch and it would extend its 3.5 meter bridge. It had to be followed by another tank to tow it out of the ditch. These were built in Leningrad in 1934.
A-1: 2: Vickers MG, 2: water cooled MG
A-2: 2: 7.62 mm MG, 2: air cooled MG
A-3: 12.7 mm (right turret), 7.62 mm MG
A-4: 27 mm (right turret), 7.62 mm MG
A-5: 37 mm (right turret), 7.62 mm MG, air cooled MG