Hoppe's Universal Bore Guide is a simple tool that makes a big difference while cleaning a firearm. It keeps bore cleaners from dripping into the action of a firearm while also preventing excessive cleaning rod contact with the inside of a bore near the chamber. The threaded brass pin locks the guide into the action in place of the bolt to allow proper cleaning from the breech. Our bore guide comes with three interchangeable chamber tips to fit a .17 caliber to a .416 caliber and the aluminum collar fits .695"/.700" (17.65mm/17.78mm) diameter bolt actions of any action length.