3 Different sizes: you will get totally 15 pieces of 100 mesh aquarium filter bags consisted of 3 different sizes in white color, including 4 pieces small size of 10 x 15 cm/ 4 x 6 inch, 8 pieces medium size of 20 x 15 cm/ 7.9 x 6 inch, and 3 pieces large size of 20 x 30 cm/ 7.9 x 11.8 inch, meet the needs of most aquarium tanks in different usage scenarios | 100-mesh filter bags: the aquarium filter bag is designed with 100-mesh fine mesh, and the mesh diameter is 150 micra, which is great to work with granulated activated carbon, peat fiber, pellets, resins or any other aquarium filter media, especially for extra-fine filter media like purigen and activated carbon | Durable zipper: the fish tank filter bag is designed with a zipper closure at the opening, which is not as easy to loosen, will effectively prevent loose media from potentially damaging to your water pump or power filter's motor or being inadvertently eaten by the fish and harming the fish | Quality material: the filter bag is made of quality nylon, and the zippers are made of quality plastic and will not rust or produce harmful substances, not affected by bleach, caustic or acid, completely safe for fish; And they are strong and durable, can be washed and reusable for many times | Inclusive usages: the fish tank filter media bag is available for freshwater and saltwater tanks, aquarium, swimming pool, pond and supermarket seafood farming occasions, also suitable for laundrying small things in the washing machine to prevent clothes from tangling