Features 1. Special design that conforms to the purpose of human mechanics. 2. Completely sealed with strong magnetic attraction. 3. Perfectly cleans dirt on the aquarium glass surface. Instructions 1. Place one half with a Velcro cleaning pad inside the aquarium and align the other half with a felt pad outside the aquarium. 2. Please be cautious when handling magnets. These magnets have very strong magnetic attraction. They should be kept out of reach of children. Sizes L - 11×6×5 cm M - 8×4×4.5 cm S - 6×2.5×4.5 cm