Densely filled polystyrene fiber. Staple set in 9″ x 2-5/8″ foam plastic block with a protective bumper. Block has one threaded and one tapered handle holes as well as a flo-thru hole for fountain type handle. Handle sold separately. Although these high-quality brushes are recommended for use on all types of vehicles, some finishes may be more susceptible to scratching than others, always test in an inconspicuous area before use.