Fluval Water Polishing Pads are uniquely designed to fit Fluval Canister Filters. These extra thick micro-fine polyester pads effectively trap micro particles and debris as water passes through. Fluval Water Polishing Pads are ideally used when cloudy water occurs or after tank maintenance to provide crystal clear aquarium water. Traps Micro Particles for Sparkling, Crystal Clear Water Ideal for Use in Cloudy Aquariums or After Routine Maintenance For Fresh and Marine Environments Maximum Mechanical Filtration For Fluval 104,105,106,204,205,206 Canister Filters