The jack - gen2 features includes a threaded bolt catch pin, reduced weight and improved styling.It is machined top to bottom from 7075-t6 aluminum with an oversized and integral trigger guard, beveled magazine flare, and a multi caliber mark.The jack is fully compatible with all mil-spec internal parts and other aftermarket mil-spec upper receivers, and gi standard issue magazines as well as pmags.Type: Lower ReceiverGun Model: AR-15Gun Type: AR PlatformCaliber: Multi-CaliberMaterial: 7075 AluminumFinish: Black Hardcoat Anodized