In case of Leopard1A3 and later variants the outer layer of spaced armor was hardened steel and the space was filled by elastomer, thus the effectiveness of shattering effect of the outer layer against APFSDS were outstanding, and the protection against early HEAT warheads were increased too. The BDD add-on armor of T-55 and T-62 series based on the same effect, but it had multiple layers within elastomer, therefore it roughly doubled the frontal protection of these tanks against APDS and HEAT weapons, and make the areas of add-on immune against HESH rounds. In T-64 and early T-72 (up to T-72M1) and T-80 (to mid T-80A) used stakloplastika (a special military-grade dense glass-fiber reinforced pressured plastic) as filling in the frontal upper glacis spaced armor. This plastic was effective in lowering the concentration of the jet of shaped charges and in destabilizing kinetic penetrators.