Fluval® Water Polishing Pads are specially designed to fit Fluval® FX4/FX5/FX6 High Performance 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. For freshwater and marine environments. Three filter pads in a pack.