Quite amazing. This is basically a small steel mesh ball, which prevents the build up of lime-scale in kettles, or 'kettle furring'. Simply place this descaling tool in any type of kettle after washing it, and limescale fur will collect on the fine stainless steel wire as the water boils. The kettle is then kept free of deposits, reducing boiling time, energy costs, and prolonging the life of the element. Just squeeze it out occasionally, as you would a scouring pad, to get rid of any limescale buildup.