IS 85
(IS 1)
IS 100, IS 122
Heavy tank
Weight: 36-48 tons
Length total: 14,4 m
Length hull: 3,38 m
Width: 4,6 m
Armour: 38 mm
Gun: 38 mm
Engine: 1200 hps
Speed: 54 km/h

The IS-1 owed much to the old KV design, but had a modified hull with improved suspension and transmission. It was heavily armoured and had a new turret, mounted an 85 mm gun (as such also called IS-85). They were now fitted with either a 100 mm gun (as IS-100) or a 122 mm gun (as IS-122). Later these vehicles were given IS-2 standards.