Aero Precision M4E1 .300 BLK Complete Uppers are equipped with CMV medium profile barrels. Along with excellent fit and finish, these AR15 Upper Receivers from Aero Precision come with Gen 2 Enhanced free-float handguards with Picatinny top rail and your choice of rail types on the other 3 faces. These solid Aero Precision M4E1 Complete Uppers are compatible with standard AR15/M4 components and have been MPI and HP tested. Get more power and accuracy when you upgrade to one of these Aero Precision M4E1 .300 Blackout Complete Upper Assemblies. Specifications for Aero Precision M4E1 16in .300 Blackout Barrel Complete Upper Receiver with Flash Hider: Manufacturer: Aero Precision Caliber: .300 AAC Blackout Overall Length: 26 in Barrel Length: 16 in Barrel Profile: DRP Gas System Length: Pistol Length Barrel Twist Rate: 1-7 Muzzle Device: A2 Flash Hider Gun Model: AR-15 Condition: New Handguard Length: 12 in Gun Make: AR Platform Barrel Material: 4150 Chrome Moly Vanadium Bolt Carrier Group Included: No Charging Handle Included: No Weight: 48.5 oz Magazine Included: No Country of Origin: USA Features of Aero Precision M4E1 16in .300 Blackout Barrel Complete Upper Receiver 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 socket 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. 16-inch 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. Standard A2 Flash Hider. Barrel nut and wrench are included. Does not include BCG or charging handle. Package Contents: Aero Precision M4E1 16in .300 Blackout Barrel Complete Upper Receiver with Flash Hider Barrel Nut Wrench