It is the wear resistance of the enameled surface, caused by the traffic of people, contact with abrasive dirt and movement of objects. The higher the PEI, the greater the wear resistance of the enamel. In non-enameled products, such as Technical Porcelain tile, PEI testing is not carried out; therefore, it does not have this classification. For these, a deep abrasion test is performed on the surface of the ceramic tiles.