A*B Arms is built stronger because sometimes, lives are on the line. Their products stand up to the rigors of combat, police and private security operations, where failure is not an option.The AR Essentials Kit includes bolt carrier group parts for the AR-15/M4 platform that can wear out or simply become lost. Manufactured to precise tolerances, these high-quality parts are MIL-SPEC, ensuring a correct fit with your AR-15 rifle. Stay prepared and keep your rifle running with the AR Essentials Kit on hand.Kit Includes: Nickel-boron coated cam pin Chrome firing pin Firing pin retaining pin Ejector Ejector spring Ejector pin Extractor spring with insert Extractor axle Gas rings "O" ring