This upper receiver features the same tried-and-true construction and aesthetics as M4E1 Enhanced Upper Receivers, without provisions for a forward assist. The M4E1 Enhanced Upper Receiver is a one-piece design combining the handguard mounting platform with the upper receiver itself. Through superior engineering, we have condensed the parts needed to mount a free-floated handguard to a mere 8 screws. Since the handguard mounting surface and upper are of the same forging, not only is it a stronger system, but we are able to make additional lightening cuts to save weight and allow for more efficient cooling. Ease of installation - Simply insert ybarrel assembly into the M4E1 upper, tighten it using the provided barrel nut and wrench, slide yrail on and tighten the rail screws. Within minutes you have a modular, free-floated rail. Specifications for Aero Precision M4E1 5.56 NATO No Forward Assist Enhanced Upper Receiver: Manufacturer: Aero Precision Fabric/Material: 7075-T6 Aluminum Caliber: 5.56x45mm NATO Gun Make: AR Platform Gun Model: AR-15 Condition: New Mount Type: Picatinny Bolt Carrier Group Included: No Charging Handle Included: No Weight: 11.28 oz Gas Port Size: 0.0785 in Gun Rail: Picatinny Country of Origin: USA Attachment Type: Picatinny Gun Type: Rifle Features of Aero Precision M4E1 5.56 NATO No Forward Assist Enhanced Upper Receiver No Forward Assist Custom enhanced forging that gives the upper receiver a "billet look" while maintaining the structural integrity of a forged part. Picatinny profile that blends seamlessly with our Enhanced Handguards M4 Feedramps .250 takedown pin holes Laser engraved T-marks Package Contents: Aero Precision M4E1 5.56 NATO No Forward Assist Enhanced Upper Receiver Port door assembly Barrel nut Barrel nut wrench This product is compatible with the following gun models: AR-15