Features For steel and aluminium. Using fibre discs is a very simple and quick solution for removing material. A low level of vibration means the tools are convenient to use. This fibre disc has been designed for general use and is made of an aluminium oxide mix. It can be used for outstanding results on steel and nonferrous metals. This fibre disc is available from our assortment in grit sizes 24 to 120. Diameter / 115x22 Grain / 120 Max. RPM / 13,300