Compatible with 6 ARC, 22 ARC, and other 6mm AR15 conversions Machined in house and assembled using only the finest steels and components.KAK Industry takes pride in producing some of the finest bolt carrier groups available, made 100% in house at our MO facility using the latest in robotics manufacturing tech* Carrier- machined from aircraft/bearing quality 8620 steel, heat treated, ground to perfection, and Nitride Finished* Profile- Full auto profile carrier with correct sear trip placement* Bolt- Machined from aircraft/bearing quality 9310 steel, heat treated properly, precision ground, and Nitride finished, MPI Tested* Firing pin- Machined from 8740, precision ground, properly heat treated, and chrome plated* Cam Pin- Nitride finished* Extractor- Enhanced Machined steel extractor - phosphate coated* Ejector- S7 tool steel ejector and extractor retaining pin* Gas Key- 4130 steel, nitride finished, precision staked using our hydraulic staking machineType II bolt faceFor 6.5 Grendel or similar