Aquarium Sponge Filter Set XY-1038

100% Polyester Non-Woven Filter Media for freshwater and marine water or outdoor pond Color: Black Dimension: 17.5 x 17.5 x 2 (thick) inch Can be cut any sizes as your needed. Cultivate the nitrifying bacteria for biological filtration. Its multi-porous feature will avoid blockages and provide the largest adhesion area for bacteria.