Aquarium Filter bag size: 20x 15cm/ 7.9 x6 inches; Mesh hole diameter: approx. 1mm, ultra-fine mesh design is perfect for use with activated carbon, peat fiber, pellets, bio-ball, zeolite, pellets, gravel, ceramic rings, ammonia remover, or any other aquarium filter media. Durable Material: The media filter bag is made of corrosion-resistant polyester material, completely safe for fish, the mesh will not be blocked by air bubbles, with no peculiar smell not affected by bleach, caustic or acid, improving the water quality and filter media usage time and efficiency. Thoughtful Design: Our plastic zipper is more safety for a media filter, reusable, and great for long-time use, differs from the metal one which may easily get rust and pollute your water. optimize your filter to meet the needs of your aquarium or pond and the fish and livestock you have. Cultivate eco water environment - Place Extra Fine Filter zipper mesh bags filled with your choice of media in flowing water. Help to create a quality living environment for your fish pet. Purified water quality, rapid probiotics cultivation, restore the high-quality water source in nature Your fish pet farming needs a good water source and management. Package comes with 10 pieces filter bags, a zipper closure design, Can be CLOSE TIGHT to prevent loose media from potentially causing damage to your water pump or power filter's motor, convenient for you to fill or empty bags.