Phosphate coating and chrome lining offer exceptional protection against wear and corrosion, making them a popular choice for those prioritizing reliability and longevity in their firearms. The phosphate coating provides a strong initial protective layer, while the chrome lining enhances durability and resistance to the stresses of repeated firing. M16 auto profile carrier machined from aircraft and bearing quality 8620 steel, properly heat-treated, precision ground and finished with a chrome-lined phosphate coating for durability and corrosion-resistance Bolt machined from a 1-piece of aircraft/bearing quality 9310 steel, properly heat-treated, precision ground, shot-peened, MPI tested and finished with a phosphate coating Firing pin machined to Mil-Spec print from 8740 steel, precision ground and chrome-plated for durability and corrosion-resistance 1-piece billet, fully machined enhanced extractor with a phosphate coating for increased reliability and corrosion-resistance Phosphate-coated cam pin S7 tool steel ejector and extractor retaining pin for enhanced strength and durability 4130 steel gas key with a chrome-lined phosphate finish, precision staked using a hydraulic staking machine for durability and secure fastening KAK carrier key screws with T25 drive, grade 8 and proper heat treatment for durability and secure fastening