Propably the most interesting was T-80B armour in turret (hull -the same as T-72A)   T-80B (1978-1984)   Psyhical thickness in the thickest place before crew comparment: 715mm psyhical thickenss at 30. degree from turret centre - 530mm psyhical thicnes in thinest place whit kvarc "sepcial armour": 520mm   Wery simple armour, heavy weight, and effective! Material thickens effectivens is well known (vs. APFSDS and HEAT)   cast steel circa 270-330HB - 0,85 vs APFSDS and HEAT