1/2 - 28 Bull Barrel Thread protector. It is machined from US made steel to very high quality standards on CNC lathes in my shop. It is counter bored to accommodate barrels that are not undercut at the shoulder. These are designed to fit great on the Ruger 10/22 with a bull barrel. With a smooth surface for a invisible look! Durable Black Oxide finish. Machined with care for a great fit and finish. Length is .440" Outside diameter is .925 With a clean smooth surface. Black Oxide finish. This thread protector works on most Ruger 10/22 with bull barrels and variants. 100% Made in the USA! Please confirm size before ordering.