The Aero Precision M4E1 Assembled Upper Receiver is designed for AR-15 pattern builds in 5.56 NATO/.223 Remington.
- Caliber: 5.56 NATO/.223 Remington
- Type: Assembled upper receiver (no BCG/CH)
- Compatible Lower: Mil-spec AR-15
- Material: Forged 7075-T6 aluminum
- Finish: Type III hard-coat anodized black
- Includes: Assembled upper with ejection port door and forward assist
- Installation: Requires barrel, barrel nut, handguard, BCG, and charging handle
