They are solid brass, which means they are soft enough to cleaning or deburring with no scrach. | Versatile kit & Commonly used for: Commonly used for cleaning,polishing,deburring of metal wood etc. | Wire wheel and end brushes are designed for easy access into narrow holes and confined areas.Cup brush is used for large area. | 1/4" shank fits most drill,4500 Max RPM;Brass wire diameter：0.13mm | Package Included:1Pc x 3" wire wheel brush;1Pcx 2.5"wire wheel brush;1Pc x 2.5"wire Cup Brush;1Pc x 1"end Brush;1Pcx 0.55"end Brush