HOPPES UNIVERSAL BORE GUIDE #UBG Keeps solvents from dripping into action & prevents excessive cleaning-rod contact with the rifling lands closest to the chamber. 3 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.