Cup brushes are used for cleaning large surfaces and removing weld scale, corrosion, rust, and paint. Brushes are usually crimped or knotted wire, with knotted wire used for more aggressive work. Crimped wire brushes can be more flexible for working irregular surfaces. Brass and bronze filaments are softer to provide a smoother finish, while carbon and stainless steel are more aggressive. Brushes filaments can be straight or flared for hard-to-reach spaces.