Mag-Float-125 Medium Glass Aquarium Cleaner (w/ scraper option) by Mag-Float Recommended for use with glass aquariums up to 125 gallons with a surface thickness up to 3/8. Features scraper attachment option (Scraper Blade sold separately). Product dimensions: (3-7/8 x 1-3/8 x 1) The Mag-Float floats when the inner magnet separates from the outer magnet. Magnet does not lose strength over time