Otis Variety Pack Receiver Brush, Nylon/Blue Nylon/Bronze The softest is nylon bristled brush, followed by slightly more aggressive blue nylon bristled brush The most aggressive of Otis' all purpose receiver brushes is the bronze bristled brush Gives you the ability to scrub places where carbon, powder and copper residue hibernate These brushes can be used on firearms, automobile detailing, boats, golf equipment Battery terminals, camping, grout, jewelry, wood working, RC hobbies, crafts and much, much more