Bore Guides are designed to align the cleaning rod with the center of the rifles bore. This insures that no damage can be done by a jag or brush. Bore Guides are machined with a snouth that extends into the chamber and seals with a silicone "O" ring at the end of the guide. This insures that solvent cannot run back into the action or trigger. ALL BORE GUIDES COME WITH EXTRA "O" RINGS! PLEASE SELECT CARTRIDGE: