Multi-Caliber Mil-Spec AR15 Lower Receiver manufactured in the USA of a high impact proprietary composite polymer. This state of the art polymer allows for superior strength unmatched durability and is extremely lightweight only 4.3oz. The AR1 eXtreme is by far the strongest composite polymer lower on the market today. The key to any good project is the foundation and on an AR15 that is the lower receiver. The Ar1 eXtreme comes with a lifetime warranty; and of course it’s Proudly American.