New Frontier’s aircraft grade anodized aluminum forged lower receivers for AR-15 rifles are consistent with mil-spec standards and compatible with all standard AR-15 components and magazines. They are shipped pre-marked with the “Safe” and “Fire” markings and include the upper tension screw located behind the grip screw. Keeping with the standard dimensions of 9.5 x 4.5 x 2 inches New Frontier lower receivers are the perfect starting point or upgrade for you next favorite AR-15 Build.