Dymax Filter Media Bag – Extra Fine – Medium With Zipper 23x14cm The Dymax Filter Media Bag – Extra Fine-Medium is a zip type filtering bag made of washable and bleachable fine nylon mesh material with a non corrosive plastic zipper which provides durability and flexibility for filtration applications The extra fine mesh is suitable for fine filter media such as: Dymax Clear mix Fine coral sand Ammonia removal resins Phosphate removal resins Great for other fine filter media like  Macropore , Purigen Features: Zip type filter media bag Durable plastic zipper Washable and bleachable nylon material Durable and stretchable Safe to use in freshwater or saltwater aquariums Extra Fine – Medium Size: 23cm x 14cm