While our standard production billet lowers will be crafted from the unique 7068 aluminum, this material has an extreme lead time for production quantities. So, to get the billet design to market, our initial lowers will be manufactured from the Mil standard 7075 alloy, aged to T651 condition, while we wait for our custom 7068 extrusions. No matter the material, Umbrella Corporation AR-15 premium billet lowers are created on GF AgieCharmilles 5-axis Mikron high performance machining centers and held to incredibly tight aerospace tolerances. Our flagship receiver, it's made to the finest standards without regard to cost. These lowers carry an unconditional guarantee against material defect and manufacturing failure. Assembly by a qualified Armorer is required.