Stripped, small pin, semi-auto lower receiver is precision machined from a durable, 7075 T6 aluminum forging. Stamped “Cal Multi,” this versatile mil-spec receiver can be the foundation for rifle builds on 5.56/.223, 6.5mm, 6.8mm, 300 AAC Blackout, 9mm Luger, or other chamberings that fit the standard AR-15 receiver. Holes, inletting and pin locations have been cut to final dimensions and accept standard AR-15 magazines and components. Clearly stamped safe/fire switch position indicators ensure that you can easily identify the service state of the rifle. Mfg: Aero Precision SPECS: 7075 T6 aluminum, hardcoat anodized. Small pin, .154″ (3.9mm) hammer/pin holes. .250″ (6.3mm) pivot/takedown pin holes. FFL required for purchase.