Otis All Purpose Receiver Brushes allows you to choose the right brush for the right project. The nylon brushes are the least aggressive, meet Mil. Spec. and are safe for everyday use. Recommended for use on virtually any surface including wood surfaces. The bronze and stainless steel brushes give you the ability to scrub hard to reach places where carbon, powder and copper residue build up. Includes 9 brushes total: three bronze, three nylon and three stainless steel.