Integral magazine well is compatible with Colt and modified Uzi style magazines. Our lower receivers feature Mil-Spec, .250 diameter take-down pins and .154 diameter fire control pins. Aircraft grade 7075 T6 aluminum billet is hard coat anodized to Mil-Spec. All internals are semi-auto, Mil-Spec. Receivers are RDIAS/RLL compatible. Receiver comes with all of the lower parts, front take-down pin, fire control group, semi-auto selector, trigger guard, pistol grip and magazine catch/release, 9mm buffer and six position stock installed.