Use, Ideal for removal of the yellow line along water line, rust stains, discoloration with more., , Application, Apply to the area you wish to treat – let remain on for 3-5 minutes – rinse with water and apply NanoPolish . The product is active by itself, which means no need to rub. In case of severe discoloration, the procedure is to be repeated until the desired result is achieved., , We recommend using protective gloves.