"The Cover Geny 10 Pieces Aquarium Filter Media Bags are designed to hold various types of aquarium filtration media. The mesh hole diameter of approximately 1.2mm makes it suitable for respiratory biological rings, activated carbon, volcanic rocks, coral sands, ceramic rings, pellets, bio-ball, gravel, zeolite, ammonia remover, and more. Please note that these bags are not suitable for finer particles. Filter bags are suitable for various filters, such as aquarium filters, tank filters, power filters, canister filter systems, canister filters, power filters, sumps, and wet/dry filters. We offer multiple sizes to choose from: 3"" x 4"", 3"" x 8"", 5.9"" x 7.8"", 10"" x 7"", and 12.2"" x 15.9"". Please select the size that best fits your needs. The aquarium filter bags are easy to use and feature a zipper closure at the opening. This design offers the convenience of easy filter material replacement and prevents any spillage of the filter material. Our bags are made of tear-resistant, strong, and durable polyester fiber material, making them durable and reusable. They can be washed and reused multiple times."