The AR-15 is a semi-automatic rifle made by ArmaLite in 1958 by Eugene Stoner. It was used in the Vietnam War, and today is a civilian version of the M-16. The AR-15 is a lightweight, intermediate cartridge magazine-fed, air-cooled rifle with a rotating lock bolt, actuated by direct impingement gas operation or long/short stroke piston operation. It has been produced in many different versions, including numerous semi-automatic and select fire variants. It is manufactured with extensive use of aluminum alloys and synthetic materials.