Combat Armory Manufacturing Mil Spec AR9 stripped Upper Receiver. Made of 7075 T6 Aluminum Billet. Large Ejection Port Hard Anodized Black Can be used for Multiple Calibers on the AR9 or AR45 Platform. This Upper is Machined to the Mil Spec. Combat Armory machinist take pride in delivering the very best for our customers used by Military, Police, and Firearms enthusiasts