Rapier is a surface-to-air missile developed for the British Army to replace their towed Bofors 40/L70 anti-aircraft guns. The system is unusual as it uses a manual optical guidance system, sending guidance commands to the missile in flight over a radio link. This results in a high level of accuracy, therefore a large warhead is not required. Rapier was later selected by the RAF Regiment to replace their Bofors guns and Tigercat missiles. It also saw international sales. It remains one of the UK's primary air-defence weapons, and its deployment is expected to continue until 2020.