The AT-4 (also AT4) is an 84-mm unguided, portable, single-shot recoilless smoothbore weapon built in Sweden by Saab Bofors Dynamics (previously Bofors Anti-Armour Systems). Saab has had considerable sales success with the AT4, making it one of the most common light anti-tank weapons in the world.The designation "CS" represents "confined space", referring to the propellant charge being designed to operate effectively within buildings in an urban environment.