9/16″X24 barrel thread and crown protector. It is machined from US made steel to very high quality standards. It is counter bored to accommodate barrels that are not undercut at the shoulder. It extends over the end of the barrel to protect the barrel crown if dropped. It has a smooth outside for a seamless look. It has 11/16″ wrench flats for easy installation and removal. It has a durable black oxide finish.