FM Products Glock Style 9mm Builders Essentials Kit includes the key components to build a reliable 9mm PCC. Each kit contains a complete FM9 Bolt Carrier Group BCG, a Heavy Buffer, and a .308 Carbine Recoil Spring to ensure proper function on a 9mm Glock Style PCC Build. The Heavy Buffer weight (approximately 6.4–6.5 oz) aids reliability in blowback operation. The kit is designed for AR-15 platform builds and is compatible with 9mm upper receivers. Features include a forged 4340 steel bolt carrier with a salt bath nitride melonite finish, and included S7 tool steel extractor and firing pin coated in nickel boron. Muzzle device used with this kit is a Micro Blast Diffuser. Package contents specify the FM Products 9mm Bolt Carrier and Heavy Buffer.