The Toolcraft 5.56x45 NATO/.223 Rem (or .300 Blackout) Bolt Carrier Group comes in the Nickel Boron finish to reduce overall wear and friction, and for upgrading your existing AR build. These Full Auto M16 Profile Direct Impingement BCG designs have multiple features that separate them from the average AR Bolt Carrier Group. They are Magnetic Particle Inspected for Quality Control, and built to Mil-Spec standards throughout. They have Mil-Spec 8740 Steel hard chromed Firing Pins, Mil-Spec Gas Keys with Grade-8 screws that are staked and sealed with Permatex No.3, and they have shot-peened case-hardened D2 tool steel extractors. These Toolcraft Inc. BCGs come from the factory with a Lifetime Replacement Warranty on the entire BCG. Plus, with the AR15Discounts satisfaction guarantee, you can buy your AR build components without apprehension. Our guarantee says if you are unhappy for any reason, you can send it back to us within 30 days for a full refund. No worries. At the time this was written, these excellent BCGs had hundreds of 5-STAR ratings from around the web making them an exquisite choice for your next 5.56 NATO/.223 Rem, .300 Blackout AR build. Get yours today!NOTE- The Nickel Boron coating is well known for reducing friction because of its molecular structure, it offers great heat dissipation properties, reduces wear on the BCG and the corresponding parts, and it increases the longevity of the BCG. Nickel Boron coatings are also known to reduce problems with function due to the decrease in overall friction and wear.Technical Specs:* Gas system: Direct Impingement* Caliber: 5.56x45mm NATO/.223 Rem, .300 Blackout* Finish: Nickel Boron Coating* Bolt: 9310 Alloy Steel (High Hardness) or Mil-Spec Carpenter 158* Carrier: 8620 Aircraft Grade Steel* Extractor: Shot Peened and Case Hardened D2 Tool Steel* Firing Pin: Mil-spec 8740 steel with hard chrome finish* Gas Key: Mil-Spec w/ properly staked Grade-8 screws and sealed with Permatex No. 3* Cam Pin: 8620 Steel w/ Black Nitride Finish* Quality Control: MPI Inspected for QC