The aquarium filter mesh bag is made of high-quality nylon material; nylon is also called polyamide fiber. Nylon has high wear resistance, high strength and good deformation resistance, anti-aging properties, the gloss of nylon fabric is brighter, the feel is smoother, and it is completely safe for fish. Polyester (polyester fiber) feels rough. The aquarium filter bag is designed with a 100-mesh fine mesh, which is a fine-pored mesh bag, and the filter material is not easy to overflow. The aquarium filter bag is designed with a plastic zipper seal at the opening. Compared with the traditional drawstring design, the plastic zipper seal not only facilitates the replacement of the filter material without rusting, but also ensures that the filter material does not overflow. Filter bags are suitable for a variety of filters including freshwater tanks, breathing bio-rings for tank filters, activated carbon, volcanic rocks, coral sand, ceramic rings and most other aquarium filter media. Reminder: Not suitable for finer powder particles. Filter bag size: 15 x 20 cm / 5.9 x 7.8 inches Package contains: 20 white zipper filter bags; enough quantity for your aquarium needs. Built to last. Washable and reusable. If you have any questions or suggestions please contact us!