Our Centerfire Cleaning Rod Guides are designed to insert into your action In place of your bolt or bolt carrier. They feature a snout with a silicone "O"-ring that inserts into your chamber, sealing the barrel off from the receiver. The "O"-ring prevents solvents from leaking back into the action area and gumming up the trigger assembly. We currently stock "O"-ring rod guides for over 1000 different action/cartridge combinations. Each rod guide is machined to fit specific actions and cartridge families from .17 up to .338 caliber. Unfortunately some rifle chamberings do not lend themselves to an "O"-ring style rod guide, for these cartridges we rec Mfg: Sinclair International