pu foam high ppi density,good flexibility ,environmental, durable, reusable Material: pu foam(polyurethane)Color : red, blue, black,colors can be done as you needDimension:can be done as you needDensity : 10-60 PPICharacteristic: void fraction can be up to 97%-99%, low flow resistance, high filter ratings, can be fire resistance and antibacterial , durable, enconomicable and environmentable