Jumbo size for jumbo tanks. Magnavore-8 is recommended for tanks over 240 Gal. Designed for fresh water and marine, acrylic and glass aquariums. Extra large 4" x 2 3/4" cleaning area rapidly removes algae on glass or acrylic aquariums 3/4" to 1" thick. Same great features as our smaller magnets. Highest quality materials and a one year defect warranty.