Never content to settle on the mil-spec, we manufactured enhancements directly into the receiver:The receiver is trued (blueprinted) by Faxon at the factoryWe hone the inside bore to smooth out the action of the bolt carrier group.Hollow-out the shell deflector to reduce weight and look greatManually engraved T-marks on the upper. Will stay visible after any coatingHold tighter tolerance on the lugs for a better fitSpecifications:Material: 7075-T6 Forged AluminumFinish: Type III Hard Coat AnodizingCaliber Compatibility: All intermediate cartridges. .458 and large bore rounds may not function in the intermediate upper.Weight: .43 Lbs (6.88 Ounces)