This AR15 Mil-Spec M4 Style 6-Position Stock with QD Sling Swivel and Butt Pad fits original equipment, it is a drop-in replacement buttstock for AR15/M4 carbines using mil-spec sized receiver extension tubes. The AR-15 stock features deluxe a-frame and it is six-position collapsible adjustable butt stock made of heavy duty polymer. AR15 Stock has spring loaded lever lock making adjustment fast and easy. Stock has 4 points to mount QD sling swivel 1 swivel included. Stock Replacement is fast and easy just simply remove your old stock and slip new one over your mil-spec buffer tube and your done.