LTWHOME Foam Filters Suitable For Fluval U3 Filter Approx size:196mm x 60mm x 8mm These carbon filter pads are intended as an alternative to the poly/carbon cartridge, and offer excellent chemical carbon filtration in the aquarium. There is no poly side to these filters. They are just Activated Carbon impregnated foam. After market product,Not Hagen FLUVAL genuine FOAM Provides efficient water flow with less clogging for long lasting filtration