The friction material is that which covers the working surfaces of the clutch disc, the brake shoes and drum pads for disc brakes. Must have a high coefficient of friction, must be able to withstand very high temperatures with impunity and must wear the absolute minimum extent in the course of their work. Traditionally, it takes dough (or real tissues) a basis of asbestos but recently this material has been banned in all major industrialized countries because its dust is carcinogenic. Today are frequently used friction materials obtained by sintering (metal, metalloceramici). In racing cars with carbon discs are used pads of the same material.