AR-15 80% Builds

80% AR-15 Lower Receivers & Build KitsForged and billet 80% AR-15 lower receivers for your rifle build. Mil-spec dimensions, accepts any standard upper receiver and lower parts kit. Includes jig kit with tooling. Our team at Polymer80 Builds has built AR platforms from every major 80% manufacturer — we stock only the lowers that pass our tolerance checks.