Knotted cup brushes are aggressive tools and are ideal for heavy duty brushing, for example when preparing metal surfaces before painting, for removing rust, slag, scales and concrete residue for for general cleaning of large areas.  

At diameter sizes 80 mm and larger, knotted cup brushes are also available with supporting ring. It stabilised the brush and is simply removed when the free wire part is worn off. Then a further 20 mm of wire can be used. Beyond that the supporting ring prevents the lateral shifting of the material.