Features: 1.The mouth of the bag is equipped with high quality zipper, and the mesh bag with plastic zipper is nylon, which is easy to clean and maintain. Will not rust and produce harmful substances. 2.When in use, put the filter material into the mesh bag and put it into the filter tank, replace or clean the mesh bag directly and take it out. 3.The bag is suitable for holding large scale media items, such as granular carbon, biospheres, bioceramic rings, zeolite, and gravel. 4.The multi functional media bag is specially designed for filtration applications and is not suitable for fine grained carbon carbon media. It is completely safe for both freshwater and seawater aquariums. 5.Our large filter media bags fit tightly to prevent loose media from damaging your pump or power filter motor. Specification: Item Type: Filter Mesh Bag_x000D_ Material: Nylon PackageList: 4 x Net Bag Note Please allow 0.5?2cm / 0.2?0.8in error due to manual measurement. Thanks for your understanding.