Otis .50 Cal Muzzleloader Cleaning KitOtis . 50 Cal Muzzleloader Cleaning Kit Complete Bore Maintenance in One Compact System The Otis . 50 Cal Muzzleloader Cleaning Kit brings Otis's legendary breech to muzzle cleaning technology to the black powder world. Unlike traditional rigid cleaning rods that can damage your crown or introduce cleaning solvent into the action, the Otis flexible pull through system cleans from the breech end the safest, most effective direction for bore