The machined brass guide, equipped with a protective O-ring retainer, prevents damage to the rifling and coated cleaning rods. It ensures the rod remains centered and does not scrape the coating from the rod. .30 Cal brass muzzle protector Compatible with .30 Cal to .308 Cal firearms Compatible with all J. Dewey cleaning rods of .22 Cal, .27 Cal and larger Incorporates a rubber O-ring to safeguard the barrel crown