Keeps solvents from dripping into action and prevents excessive cleaning rod contact with the rifling lands closest to the chamber. ? Three interchangeable chamber tips to fit .17 to .416 caliber. ? Aluminum action collar fits .695"/.700" (17.65mm/17.78mm) diameter bolt actions of any action length. ? Threaded brass pin locks the guide into the action in place of the bolt to allow proper cleaning from the breech.