This Upper Receiver Handguard Combo now includes our Gen 2 Enhanced Handguard! Key features include the addition of quick disconnect sling sockets, enhanced milling design for grip and visual appeal and a new profile for the picatinny top rail. Anti-Rotation Tabs. Feed Ramp Extension. Scalloped Rails. Continuous Top Rail. Specifications for Aero Precision M4E1 AR-15 14.5in 5.56 Mid Barrel Complete Upper Receiver with Flash Hider: Manufacturer: Aero Precision Caliber: 5.56x45mm NATO Gas System Length: Mid Length Barrel Twist Rate: 1-7 Handguard Type: Free-Float Muzzle Device: A2 Flash Hider Gun Model: AR-15, M16 Condition: New Fabric/Material: 7075-T6 forged aluminum Attachment Type: Picatinny Handguard Length: 12 in Gun Type: Rifle Gun Make: Aero Precision, AR Platform Included Accessories: Standard Barrel Material: 4150 Chrome Moly Vanadium Gas Block Journal Size-Length: 0.75 in Bolt Carrier Group Included: No Charging Handle Included: No Magazine Included: No Mount Type: Picatinny Country of Origin: USA Features of Aero Precision M4E1 AR-15 5.56 Mid Barrel Complete Upper Receiver with Flash Hider: Forged from 7075 T6 aluminum; Precision machined to M4E1 specs; M4 feedramps; Matte black hard coat anodized Mil 8625 Type 3 Class 2; Laser engraved T-marks (Anodized only); Comes assembled, with port door and forward assist installed; Handguard mounting platform is forged into the receiver; Works with Aero Precision handguards but also fits most BAR-system handguards; Features of Gen 2 Enhanced Handguard Features: 1pc free float design; Built in anti-rotation tabs; Scalloped rails; Continuous top rail; 1.78" inside diameter fits most muzzle devices and 1.5" suppressors; Compatible with low profile gas blocks; Quick disconnect 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 the continuous picatinny top rail Features of 14.5in 5.56 Mid-Length Barrel Features: 5.56 Nato Midlength, 1/7 twist, 4150 CrMoV, QPQ, gas port drilled; .750 gas block journal; Midlength gas system, .0785 gas port; M4 Feed Ramp Extension; HP and MPI tested; Standard A2 flash hider Package Contents: Aero Precision M4E1 AR-15 14in 5.56 Mid Barrel Complete Upper Receiver with Flash Hider Enhanced Handguard 5.56 Mid-Length CMV Barrel Low Profile Gas Block and Mid Length Gas Tube Barrel nut and wrench Which weapon models is Aero Precision M4E1 AR-15 14.5in 5.56 Mid Barrel Complete Upper Receiver with Flash Hider compatible with? Aero Precision M4E1 AR-15 14.5in 5.56 Mid Barrel Complete Upper Receiver with Flash Hider is compatible with AR-15, M16