Water Polishing Pad, 3 Pack for Hagen Fluval 304, 305, 404 and 405 canister filters. Fluval part A-242For freshwater and marine environments4-3/8" X 3" X 1-3/8"Fluval Water Polishing Pads are uniquely designed to fit Fluval canister filters. These extra thick micro-fine polyester pads capture micro particles as the water passes through. Use Fluval Water Polishing Pads when the water is cloudy.