1>PU sponge good for aqaurium filtering 2>good air permeability 3>Polyether sponge, reticulated ; open cell PU sponge widely used in aquarim filtering, water filtering, air filtering, packing and other business .The polyurethane foam filterhas different mesh(8ppi-60ppi), high resilient ,good colors and good air permeability .Widely used for aquarium filter, water pump and other filtering business ...