The Geissele Stressproof Bolt is the same bolt proudly featured in the Reliability Enhanced Bolt Carrier Group. The Forged Stressproof Bolt is made from Carpenter 158+, directly developed with Carpenter Steel metallurgists to create a material that is cleaner and has less impurities. This makes the Stressproof Bolt stronger and more fatigue resistant, capable of 5 times the life of a mil-spec bolt. Each Forged bolt is rigorously inspected, high pressure tested, mag particle inspected and Nanoweapon coated. IncludesGeissele Stressproof BoltExtractorExtractor SpringExtractor O-ring and insertEjectorEjector SpringEjector Pin