You are purchasing 4 x Finest Filters Compatible Polycarbon filter cartridges suitable for the Fluval U4 aquarium filter.
Our polycarbon filter cartridges have a white polyester side for mechanical filtration, and a black carbon impregnated side for chemical filtration of the water.
Please Note: These are NOT original spare parts - these are compatible filters manufactured by Finest Filters.
Plain foam filter pads also for sale in our eBay shop!