These Neodymium rare earth magnet discs are coated in a black epoxy finish and incredibly small. but in grade N40 they are very powerful, even though these Rare earth magnets are tiny, just one will hold a sheet of 8 1/2" x 11" paper to a fridge or filing cabinet. We also sell a magnet that is the same size and shape as this one but coated with a nickel plating (silver in color).