... Smooth Surface3.no toxic.durable in water ,could filter air,dustExtruded polythylene foam could stand some press ,closed cell .,10- ... ,good elasticiry ,no toxic.durable in water ,could filter air,dust.1 .pu foam material2, reticulated, mesh,10ppi-60ppi,3 good resilient ... ,durable in water . 5 widely used in aquarium filter ,water filter ,air filter ,water pump,medical machine,cleaning kitch and dish ect ...