These discs are made by coating aluminium oxide grains over a cloth backing to form a fan like configration, thus creating a long lasting, cooler running disc. These are used mainly for blending and applying touches to edges and for treating flat and mildly countoured surfaces, cleaning of alloys etc. Also used for removing rust. And they need not be changed when used to treat different kinds of materials as fresh layers of abrasives are constantly being exposed as they are used.