The 9K31 Strela-1 is a mobile, short-range, low altitude infra-red guided surface-to-air missile system. Its NATO reporting name is SA-9 Gaskin. Each unit consists of two pairs of ready-to-fire 9M31 missiles mounted in boxes on either side of a turret on a BRDM-2 amphibious vehicle.Development of the SA-9 Gaskin in the Soviet Union was based on a requirement for a regimental vehicle-mounted SAM to support the ZSU-23-4. The Strela-1 is deployed in the short-range air defence battery of Soviet motor rifle and tank regiments. The battery consists of a gun platoon of four ZSU-23-4 Shilkas, and a SAM platoon four Strela-1 vehicles. It is no longer in service in Russia.