The Aero Precision EPC/AR9 Bolt is the core of your EPC build. Machined from 8620 steel and featuring a nitride finish, fracture resistant grade 23 titanium pin, and 4140 steel extractor, the EPC bolt assembly is precision machined from the ground up to meet the extreme demands of blowback AR platform firearms. FeaturesMachined from 8620 SteelBlack Nitride Finish Includes8620 Steel Bolt Assembly4140 Steel Bolt GuidesGrade 23 Titanium Firing PinFiring Pin Retaining Pin4140 Steel ExtractorHeavy Duty extractor coil pin(all parts are installed) Disclaimer: Aero Precision's 9mm Bolt may not be compatible with some aftermarket fire control groups. It is recommended to use a mil-spec or PCC specific trigger group. After assembly, verify proper operation and trigger reset with an unloaded firearm prior to use. This bolt is not compatible with most AR15 folding stock adapters.