Chamber: 5.56 NATO. PRO anodized black lower receiver has ambidextrous safety, magazine release, and bolt catch. Barrel is a Ballistic Advantage cold-hammer-forged 16″ chrome-lined unit in an Aero Precision MOD 4 slimline handguard. Chrome-lined phosphate M16-cut bolt carrier group w/ C158 tool steel bolt assembly. Mid-length gas system, pined low profile gas block, HPT & MPI tested. EZ install takedown/pivot pins, ALG QMS single-stage trigger, Magpul MOE Grip & MOE SL Stock. Kodiak brown and OD Green anodized finishes also available.