The MGM-166 LOSAT (Line-of-Sight Anti-Tank) was a U.S. surface-to-surface missile system designed by Lockheed Martin (originally Vought) to defeat tanks and other individual targets. Instead of using a High Explosive Anti-Tank warhead like other anti-tank missiles, the LOSAT employed a solid steel kinetic energy penetrator to punch through armor. The LOSAT is fairly light; it was designed to be mounted onto a Humvee while allowing the vehicle to remain air-portable. LOSAT eventually emerged on an extended-length heavy-duty Humvee with a hard-top containing four KEMs used by special operations. Although LOSAT never "officially" entered service, it was used for the smaller Compact Kinetic Energy Missile.