This Spike's Tactical Bolt Carrier Group is the same Mil-Spec BCG that they sell but the only difference is that it's coated in Nickel Boron. It is High Pressure Tested and Magnetic Particle Inspected (HPT/MPI). Nickel Boron has proven itself to be the most durable finish on the market. It's much smoother than Hard Chrome, it's easier to clean, makes the rifle cycle smoother, it can be run almost lube free for thousands of rounds, and it will never chip, peal, or flake off. This BCG works in AR-15s. This BCG does NOT make your rifle fully-automatic. It is machined from 8620 Tool Steel (Carrier) and 158 Carpenter Steel (Bolt) and has a shrouded firing pin. It has Nickel Boron Coating inside and out (Bolt, Carrier, and Gas Key). The Forged Mil-Spec gas key is attached with Grade 8 hardware and properly staked. The bolt is shot peened. It has Mil-Spec Extractor Spring, black extractor insert, Viton O-Ring and Tool Steel Extractor.