SPECS: Receiver/Handguard/Gas Block/Charging Handle – 6066 T6 aluminum, anodized and teflon coated, black. Bolt/Carrier – 4140 steel, parkerized, matte black. Barrel – 4140 chrome-moly steel, parkerized, matte black, or 416 stainless steel, natural finish. Fits DPMS LR-308 lower receivers only.