Aero Precision's state of the art M4E1 platform starts here, with the M4E1 Upper Receiver. The M4E1 upper receiver is a one-piece design combining the handguard mounting platform with the upper itself. Through superior engineering, Aero 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 they are able to make additional lightening cuts to save weight and allow for more efficient cooling. Ease of installation - Simply insert your barrel assembly into the M4E1 upper, tighten it using the provided barrel nut and wrench, slide you Mfg: Aero Precision SPECS: Material: Forged 7075 T6 Aluminum with hard coat anodized finish.