The BCM SOPMOD Bolt Upgrade/Rebuild Kit provides everything needed to upgrade or rebuild your AR-15/M16 bolt carrier group with mil-spec components and enhanced reliability features.BCM SOPMOD Bolt Upgrade/Rebuild KitExtractor: Made to USGI specifications with shot peening treatmentBCM Extractor Spring: Chrome silicon construction heat treated stress relieved and shot peenedGas Rings: 3 USGI specification gas rings includedCrane Industries O-ring: Military specification sealing ringBlack Extractor Insert: Complete with extractor pinIdeal for maintaining peak performance in your rifle platform this comprehensive kit ensures reliable extraction and proper bolt function for both recreational and professional applications.