FILTER BAG SIZE: 10 Pcs (15 x 20 cm / 5.9 x 7.9 inches), 10 pcs (20 x 30 cm / 7.9 x 11.8 Inches). The diameter of mesh hole: 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 THOUGHTFUL DESIGN: Zipper is plastic, you do not worry it would rust and produce harmful substances, it great for use in canister filter system, also can be used as laundry bags, storage bags MESH BAG MATERIAL: Nylon, polyamide fiber; high wear resistance, high strength and good resistance to deformation, anti-aging, completely safe for fish ADVANTAGES: 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 SERVICES: We pride ourselves on that. We want you to know that you matter to us here. We would offer you 100% risk-free satisfaction guarantee to let you buy with confidence. YOU are our number one priority