Listed on PA's site: "The Hammerhead Float. Our NEW best seller! Not only cleans great, but floats back to top if it looses contact. This is our most popular cleaner and best bet for larger tanks, also the best bang for your buck With a large 4" x 2" cleaning area it will turn large jobs into a fun and effortless task. Its extremely powerful magnets will clean tanks from 75 to 250 gallons, with glass thickness up to 1/2 and 5/8" and acrylic thickness up to 3/8 and 1/2". "