Your bolt carrier group is one of the most critical parts of your build. Don't buy an imitation. This is the same BCG Spike’s uses on their builds. The Spike's Tactical Lightweight BCG is one of the finest bolt carrier groups on the market, built from mil-spec 8620 tool steel and high pressure tested and magnetic particle inspected for durability and reliability. These Bolt Carrier Groups by Spikes Tactical have shot peened bolts that are CNC machined from 158 carpenter steel, and a mil-spec tool steel carrier key that is expertly attached with grade 8 hardware and properly staked. The Spike's Tactical AR15 Bolt Carrier Group is complete with a mil-spec tool steel extractor, a black extractor spring insert, and a Viton o-ring. When you need a high quality, durable bolt carrier, choose the Spike's Tactical Advanced Bolt Carrier Group.