These Aero Precision M4E1 Complete Uppers with 8in .300 Blackout Barrels are equipped with Chrome Moly Vanadium barrels. Along with solid fit and finish, these AR15 Upper Receivers from Aero Precision come with Gen 2 Enhanced free-float handguards with Picatinny top rail and a choice of rail types on the other 3 faces. These Aero Precision M4E1 Complete Uppers have been MPI and HP tested and are compatible with standard AR15/M4 components. Get more power, precision and accuracy when you upgrade to one of these Aero Precision M4E1 8in .300 Blackout Complete Upper Assemblies. Specifications for Aero Precision M4E1 8in .300 CMV Barrel Complete Upper Assembly with Flash Hider: Manufacturer: Aero Precision Caliber: .300 AAC Blackout Barrel Length: 8 in Muzzle Device: A2 Flash Hider Gun Model: AR-15 Condition: New Fabric/Material: 416R Stainless Steel Handguard Length: 7 in Handguard Style: Quad Rail Magazine Included: No Country of Origin: USA Features of Aero Precision M4E1 8in .300 CMV Barrel Complete Upper Assembly with Flash Hider: Forged from 7075 T6 aluminum. Precision machined to M4E1 specs. M4 feedramp extension. Comes assembled, with port door and forward assist installed. .300 Blackout for more power - compatible with standard AR15/M16 components. Handguard mounting platform is forged into the receiver. Works with Aero Precision handguards but also fits most BAR-system handguards. Gen 2 Enhanced Handguard Features 1-piece free float design, built in anti-rotation tabs, scalloped rails, continuous top rail, 1.78-inch inside diameter fits most muzzle devices and 1.5-inch suppressors, compatible with low profile gas blocks, QD sling sockets at the 3, 6 and 9 o'clock positions, additional milling along flats to aid with gripping and add visual appeal, new profile for continuous Picatinny top rail. Barrel made of 4150 Chrome Moly Vanadium with QPQ corrosion resistant finish. Low Profile Gas Block and Pistol Length Gas Tube. HP and MPI Tested. Barrel nut and wrench are included. Does not include BCG or charging handle. Muzzle brake that comes with this complete upper receiver is NOT pinned nor welded to this barrel. Per the National Firearms Act, the muzzle brake MUST be pinned and welded to achieve the necessary 16 inches as defined by the ATF for a rifle build. Package Contents: Aero Precision M4E1 8in .300 CMV Barrel Complete Upper Assembly with Flash Hider Barrel Nut Wrench Which weapon models is Aero Precision M4E1 8in .300 CMV Barrel Complete Upper Assembly with Flash Hider compatible with? Aero Precision M4E1 8in .300 CMV Barrel Complete Upper Assembly with Flash Hider is compatible with AR-15