 In the 1980s, 3UBM11 antitank rounds were introduced, with 3BM25 armour-piercing fin-stabilized discarding-sabot (APFSDS) tungsten carbide penetrator, which increased its armor penetration.In 1983, the T-55M and T-55AM tank upgrade program also added the ability to some tanks to fire the 9K116-1 "Bastion" guided missile system (NATO reporting name AT-10 Stabber), for long-range engagements of tanks and low-flying helicopters.The anti-tank missile is encased in the 3UBK10-1 shell, which is handled, loaded, and fired exactly like a conventional tank gun round.