This is a replacement pad for the Tunze aquarium cleaners. The TUNZE magnetic pane cleaners are used for cleaning aquarium panes. On account of the casing they are corrosion resistant and may remain in the aquarium without any adverse effect on your aquarium biotope. They consist of an inner section with a rough surface and an outer section with a felt or velour surface. The two sections are connected with the retaining cord supplied along with the unit to allow easy retrieval, if they separate.