Faxon Firearms Bolt Carrier Group, 5.56NATO, Fit AR-15, Salt Bath Nitride Finish, Black FF556BCGCNITRIDE The Faxon 5.56 M16 Bolt Carrier Group" Nitride is a high-performance and reliable upgrade for your AR-15 rifle. This bolt carrier group is designed for optimal performance and is made from top-quality materials" ensuring durability and longevity. The nitride finish on the carrier and bolt provides added corrosion resistance" making it a great choice for use in harsh environmental conditions.