One piece Past The Barrel (PTB) adapter for ops inc 12th model, AEM5 and OCM5. Made from H900 heat treated 17-4 steel this one piece mount will allow you to mount your silencer to any 1/2A-28 barrel that the O.T.B. adapter will not. Barrels with a OD larger than .75 or less than 2.95 inches of exposed barrel. This mount will add 2.90 to your overall system length. Made with integrated wrench flats in the rear for easy installation or removal with any adjustable crescent wrench. Because these set the end cap exit so far away from the muzzle we recommend always checking with an alignment rod. If your barrel threads are not perfect with this mount + a tight bore silencer you could get end cap strikes if not checked.