Cryptic Coatings specializes in bolt carrier groups and BCG coatings. Our PVD and CVD processes are designed to provide reduced friction, lower operating temperatures and increased overall performance and BCG life. Our bolt carrier groups are backed by our lifetime warranty. Should our products fail to function properly, return it for a brand new replacement. We also carry all necessary replacement pieces for your manganese phosphate AR-15, M-15/M-16 or M-4 bolt assembly.