BACK IN STOCK! Newly manufactured. This new version is lighter than the original nut (1.4oz vs 4.5oz) and is made of T60/61 Aluminum. This proprietary PATENTED barrel nut is compatible with the Adams Arms piston system among many others. If used with the XLP Piston Block from Adams Arms, there is no need to remove the hand guard to adjust the piston. Just insert a small Allen Wrench or plastic stylus (not included) into one of the holes on the rail that lines up with the adjustment selector. Precise timing not required. Just insure that the piston rod stop is seated on the barrel nut and catches the lip of the nut. Included with this barrel nut is a timing shim kit. Piston kit or rod not included.