Magnolia Brush filling material is staple set in foam plastic block. The 10-inches blocks have one threaded and one tapered handle hole. These brushes are acid-resistant. 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. Will accommodate flo-thru handle. 2-1/2-inches trim length. Polystyrene is highly resistant to acids and detergents, but has a lower resistance to petroleum solvents. Polystyrene has excellent flexibility and wear ability.