The AR style Bore Guide with O-Ring inserts in place of the bolt carrier group assembly while cleaning to center cleaning rod and prevent chamber or muzzle damage. O-Ring seal at breech prevents solvent from entering the upper receiver and trigger mechanism while also keeping chemicals out of the action. Solvent Port makes using CLP/Cleaner fast & easy. Superior Delrin Bore Guide- Chemical resistant and will stand up to harsh chemicals, providing continual use. Reusable Tube with Hang Cap Made in USA