SN: M4CE14021. Modern production, 5.56mm with a 14.5″ barrel w/pinned & welded flash hider. Bore is bright with strong rifling. Semi-auto tactical carbine with a quad rail handguard w/Knights Armament covers, front sight post, Troy Ind. flip-up rear sight, and ambidextrous selector controls. Near excellent condition overall. Comes with box.