Description Aero Precision M4E1 Stripped Lower receiver for AR15, multicaliber for 5.56, .223, and .300 AAC Blackout. Forged aluminum receiver with black anodized finish. Integrated trigger guard and increased magwell flare. Comes in its factory box. Must ship to a FFL holder. Condition: New in box. Serial: M4-0147923 Manufacturer: AERO PRECISION USA Caliber: Multi Model: M4E1 Book# 03261