Double End Nylon & Bronze Combinations Set Firm bristles safely clean hard-to-reach areas in vent ribs, trigger assemblies and receivers. For added utility, it is double ended with larger bristles on one end and smaller, stiffer bristles on the other. The white nylon bristles are rugged and solvent resistant. The bronze bristle brush is great for removing stubborn fouling. Features: Firm Nylon & Bronze Bristles Solvent Resistant Made in USA