The Dymax Mag-Scraper is a floating magnetic cleaning and scraping device that makes aquarium maintenance easier and faster without the need to put your hand in the water. This product is made from strong and reliable materials suitable for use in both freshwater and saltwater aquariums. The Mag-Scraper includes attachable plastic scraping blades that help remove algae or stubborn debris from the glass surface. Size L: For glass thickness 16-20 mm