The TUNZE magnetic pane cleaners are used for cleaning aquarium panes. The TUNZE 0220.550 Power Magnet has been developed especially for the requirements of glass thicknesses of 3/8" to 1 1/8" 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.