SPECS: Reinforced molded polymer, Black, Dark Earth, OD Green, or Foliage Green. Fits AR-15/M16/M4 rifles with buffer tube for M4-style adjustable buttstock, carbine-length gas system, Delta ring, and standard A2 gas block/front sight base. Buffer tube, carbine buffer, receiver extension nut, and carbine-length action spring not included. Mil-Spec fits rifles with Mil-Spec 1.14” O.D. buffer tubes. Universal fits rifles with commercial 1.17” O.D. buffer tubes.