The red brush has very stiff bristles and is meant for intense scrubbing of hard surfaces. Use it in removing heavy grease, grime, old, loose paint and blisters, aggregate, barnacle stains on boat hulls, propellers, rudders and shafts, etc. Safety Tips: Always wear face and body protection. Be sure that the brush's steel insert shaft is firmly fastened in the drill chuck. Always use a properly grounded machine. Maximum RPM 3,500 5" Diameter 1ea.