The Firepower 1423-2118 Knot Type Crimped Wire End Brush has a 1-1/2-inch diameter, a 1/4-inch shank, 0.020-inch carbon steel wire size and a 20,000 maximum RPM. Firepower small diameter wire brushes are designed for use in restricted or hard-to-reach areas. They are excellent for debarring, blending and cleaning of surfaces. Small diameter brushes are especially designed for use on portable air and electric tools. End brushes are great for cylinder heads, pistons and valve ports, rubber and plastic flash removal, removal of rust, paint scale, tool polishing and weld cleaning.