Designed to fit Fluval canister filters 104/105 and 204/205. These extra thick pads capture micro particles and debris. Designed to fit Fluval canister filters 104/105 and 204/205. These extra thick micro-fine polyester pads capture micro particles as the water passes through. Use when cloudy water occurs or after tank maintenance for crystal clear aquarium water. Effectively traps micro particles and debris. For crystal clear aquarium water. For freshwater and marine environments. To use, rinse pad thoroughly before inserting in filter. Place pad in the last chamber, above the BioMax media (sold separately). Pads should be changed every 7-10 days (or sooner if pad becomes clogged and filter's flow rate diminishes). Comes three pads per package. Each pad measures 5.5"L x 3"W x 1.25"D.