4" Diameter Medium Grit Nylon Flap Brush with 1/4" Shank Great for Paint Removal Nothing removes rust, paint, corrosion and general schmutz like a nylon flap brush. Just smacks the stuff off. This one has (6) sets of medium grit nylon bristles and a 1/4" shank for your electric drill. Measures 4" dia and you can spin it at up to 2500 rpm.