Detailed Product Description sponge air filter/Aquarium filter /bio-filter1.polyurethane foam material2.no harmless,no toxic,environment protection3.good resilient,good air premeability4.could keep the colour for long termThe polyurethane foam filter has different mesh(15PPI,30PPI,35PPI,40PPI,60PPI),with high resilient ,many colors and good air pemeability. It is durable in water and low cost.