These Possum Hollow bore guides are machined from a solid piece of delrin, a 100% solvent resistant material. These 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.
The o-ring guides are machined with a snout that extends into the chamber. This snout has a silicone o-ring that seals off the chamber. This insures that no solvent can run back into the action or trigger.