Feature- Hole Size: S- Material: Biochemical cotton.- Color: Black.- Size: Approx. 50 x 50 x 2 cm.- This fish tank filter has three pore sizes, small hole/ medium hole/ large hole.- Placing filter cotton in the fish tank can reduce the residue floating in the water, improve the survival rate of fish, and at the same time increase the oxygen concentration of the fish tank.- This fish tank filter has great filtering and adsorption capacity. It can still be used after cleaning.- Filter cotton can be used in most fish tanks, suitable for freshwater tanks, seawater tanks, and aquatic plants.- This is a great aquarium filter cotton to use to create a fresh environment for your fish to bring home. Package Including 1 x Filter Cotton