The Anderson Manufacturing M16 5.56 Complete Bolt Carrier Group features a 9310 steel bolt and 8620 steel carrier. The bolt is magnetic particle inspected (MPI), and the extractor includes an O-ring insert for positive extraction. Carrier and gas key are chrome lined, and all components feature a matte black phosphate finish. Gas key screws are properly torqued and staked. Complete Group includes: Bolt, Extractor, Extractor Spring/Buffer, Extractor O-Ring, Extractor Pin, Firing Pin, Firing Pin Retaining Pin, Gas Key & Screws, Carrier, Ejector, Ejector Spring, Ejector Roll Pin, and Cam Pin. Mfg: Anderson Manufacturing SPECS: Fits - AR-15 or M16 rifles. All NFA rules apply.