The more advanced late cold war tanks were given multi-layer skirts (Leopard 2), in which passive (or reactive) effects significantly reduced the effectiveness of HEAT ammunition. At the same time, these elements are already heavy and have considerable thickness, which increase the size and weight of the vehicle and make maintenance difficult. Russian and some western tanks carries explosive-reactive armor blocks in order to increase effectiveness of spaced armors (particularly in case of side skirts, e.g. TUSK, T-90), and main frontal armor.