Fluval Carbon Impregnated Foam Pads are specially designed for Fluval FX 4, FX5 and FX6 High Performance Canister Filters. These carbon impregnated pads capture micro particles as the water passes through. The added carbon removes odor, discoloration, as well as heavy metals and organic contaminants. Protects Aquarium Filter Motor By Trapping DebrisAdded Carbon Removes OdorsHelps Keep Water Crystal ClearFor Freshwater and Marine EnvironmentsFor Fluval FX4, FX5 and FX6 High Performance Canister Filters INSTRUCTIONS: Rinse frequently, replace every month