Friction plates are composite materials with complex structures. Due to their composite nature and production process, the appearance characteristics of precisely designed products make the products unique. The appearance characteristics of a well-designed product are clear. This standard defines appearance factors for identifying and evaluating product characteristics in quality assurance and serves as the basis for commercial and technical agreements. Product features are listed in no particular order. If a brake lining is in "as supplied" condition, it means that the lining has not been used. Among some features, the brake lining requirements are different for effective lining areas <120cm² and ≥120cm². The acceptance criteria of this standard are that it is not permitted to impair the functional and performance characteristics of the brake lining, unless otherwise agreed between the supplier and the purchaser.