Based on the SOPMOD designed bolt upgrade and rebuild package, this Bravo Company SOPMOD Bolt Upgrade Rebuild Kit is designed to breathe new life into your bolt assembly. The bolt assembly is the heart of your AR15 rifle system and preventative maintenance used by professionals insures these systems keep running even under the harshest of conditions.This is a great spare parts kit to keep your AR15, M16, M4 running in the field.Kit includesExtractor made to USGI specs (shot peened)Extractor pinBCMA(R) Extractor Spring (chrome silicon, heat treated & stress relieved, shot peened)3 USGI Gas RingsCrane Ind O-Ring (Mil-Spec)Black Extractor Insert