The Two-Piece Bolt Carrier Group.The Two Piece BCG is designed to be manufactured on modern equipment using modern materials. Q's BCG consists of 2 sections; The Front-End and The Ass-EndThe front end is made up of Maraging Stainless Steel dressed in black with a Nitride Coating and is SCAR-Cut to help prevent bolt bounce. Standard with: Mil-Spec Gas Key and Staking Mil-Spec Bolt Mil-Spec Cam Pin Mil-Spec Firing PinThe Ass-End is naked Stainless Steel heat treated of course and yes the overall length is Mil-Spec.The Ass-End holds the firing pin doing away with pesky firing pin retaining pins. No more broken pins. You're welcome. The Carrier is retained with a single Pin allowing for easy field stripping.