The Aero Precision M4E1 18″ 5.56 Complete Rifle is built on our popular Enhanced Series Upper Receiver. This system features a custom integrated upper receiver and handguard platform that provides the shooter a light-weight, free-floated, rigid design resulting in superior performance and accuracy.All complete rifles are assembled by our professional gunsmiths and are tested prior to leaving our facility. Buy with confidence when you purchase an Aero Precision Complete Rifle.Upper Features:Upper: M4E1 Enhanced Upper ReceiverBarrel: 18″ 5.56, Rifle Length, 1:7 Twist, 4150 Chrome Moly Vanadium, QPQ corrosion resistant finishHandguard: Gen 2 Enhanced Series Handguard of choiceGas System: Low Profile Gas Block and Rifle Length Gas TubeBolt Carrier Group: M16 Cut, 8620 Steel, Phosphate Finish, Properly StakedMuzzle Device: Standard A2 Flash HiderLower Features:Lower: Gen 2 Lower Receiver with flared magwell and tension screwLower Parts Kit: Standard AR15 Lower Parts Kit w/ Billet Trigger GuardBuffer Kit: Standard Mil-Spec AR15/M4 Buffer KitStock: Magpul STR StockGrip: Magpul MOE GripMagazine: Magpul 30 Round PMAG(R)Availability subject to applicable federal, state and local laws and regulations. Always have full knowledge of your state and local gun laws before attempting to order or purchase a gun. Any orders returned due to legal restrictions are subject to a 10% restocking fee.We currently do not ship this product to the following states: California, Colorado, Connecticut, Hawaii, Illinois, Maryland, Massachusetts, New Jersey, New York and Washington D.C.