Dymax Filter Sock is a mechanical filter bag, ultrasonic constructed with high durability material such as polypropylene and polyester that has high filtering efficiency, oil removal capability and high dirt loading capacity.  This product is fully washable and reusable many times.  Its high range of micron effectively removes fine to large debris from the water and thus provides crystal clear water for both fresh and salt water aquariums.7″. 200 Micron.