Dark Storm Industries DS-15 Mil-Plus MFR Dual Ejector AR-15 .300 AAC Blackout/5.56x45mm NATO Bolt Carrier Group Black. This bolt carrier group uses the best US produced metals and is held true to the strict Mil-Spec dimensional tolerances with 100percent quality control inspection of over 100 points in the machining process. Dark Storm Industries does not do "batch" inspections where only a few parts are checked. This process takes more time and results in more scrap but the result is every part is in spec. The bolt features the enhanced geometry changes with an increased radius on the rear of the lugs which reduces the stress concentrations at the most common point of failure. The bolt also features an increased body diameter around the cam pin to reduce bolt stretch at the second most common failure point. Together these changes provide as much as a 50percent increase in bolt life while remaining compatible with standard Mil-Spec bolt carriers and barrel extensions. All parts are properly heat treated and finished per the Mil-Spec. Don't be fooled by cheap nitride finished bolt carriers. The Mil-Spec prohibits the use of nitriding (Note 9.B.4) for a reason. All components are finished with (DLC) Diamond Like Coating for corrosion resistance and hexavalent hard chrome for heat and wear resistance in critical areas. Dark Storm Industries does not high pressure test our commercial bolts as doing so reduces the operational life span. The bolts and bolt carriers are marked with lot numbers to provide full traceability of material machining heat treatment and finish. Specifications for Dark Storm Industries DS-15 Mil-Plus MFR Dual Ejector AR-15 .300 AAC Blackout/5.56x45mm NATO Bolt Carrier Group: Manufacturer: Dark Storm Industries Color: Black Finish: DLC Carrier Material: Steel Bolt Material: Steel Caliber: 5.56x45mm NATO .300 AAC Blackout Gun Make: AR Platform Gun Model: AR-15 Length: 7.75 in Weight: 11.5 oz Features of Dark Storm Industries DS-15 Mil-Plus MFR Dual Ejector AR-15 .300 AAC Blackout/5.56x45mm NATO Bolt Carrier Group Lifetime warranty Fully Transferable No Registration or Proof of Purchase Required Package Contents: Dark Storm Industries DS-15 Mil-Plus MFR Dual Ejector AR-15 .300 AAC Blackout/5.56x45mm NATO Bolt Carrier Group What firearm models does the manufacturer say Dark Storm Industries DS-15 Mil-Plus MFR Dual Ejector AR-15 .300 AAC Blackout/5.56x45mm NATO Bolt Carrier Group is compatible with? The manufacturer says that Dark Storm Industries DS-15 Mil-Plus MFR Dual Ejector AR-15 .300 AAC Blackout/5.56x45mm NATO Bolt Carrier Group is compatible with AR-15Dark Storm Industries DSI-BCG-556-DE-DLC: DS-15 Mil-Plus MFR Dual Ejector AR-15 .300 AAC Blackout/5.56x45mm NATO Bolt Carrier Group Black