Pumie sticks are amazing for cleaning "metal" markings off your porcelain toilet, toilet tank lid, sink, toilet bowl, bathtubs, etc. Use it in the bathroom or in the kitchen if you have a porcelain sink. Simply hold the stick under water to get it wet, and then apply a little pressure back and forth over the spot that has a mark. You will think that you are tearing up the surface, but after you look, the defect is gone and your porcelain is restored to new. For big areas, keep running water over the surface to ensure the pumie stick remains wet. This product combined with CeramaBryte will clean just about any stain or mark you can find on porcelain.