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. NOTE: Requires a lower parts kit buffer & stock of your choosing to complete.