The STS (Short Throw Safety) AR-15 Lower Receiver features the same specifications as Aero Precision’s standard lower receiver, but is designed to accept Short Throw Safeties, such as the Battle Arms Ambidextrous-Short Throw 45 (100-009-866). Clearly stamped safe/fire switch position indicators, with the fire location at 45/60/90 degrees, ensure that you can easily identify the service state of the rifle. 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 Mfg: Aero Precision SPECS: 7075 T6 aluminum, hardcoat anodized, matte black. Small pin, .154″ (3.9mm) hammer/pin holes. .250″ (6.3mm) pivot/takedown pin holes. FFL required for purchase.