The item is 4pcs simple and practical aquarium filter materials, which is excellent for oxygenating your water and helping the gas exchange process. So they are great for any freshwater fish tank or aquarium. And keep the water clean, improving the water quality. Features - Color: Yellow. - Material: quartz sand. - Size: About 16.00X3.70X3.70cm/ 6.29X1.45X1.45inch. - This aquarium filter media provides mechanical filtration to capture fine particles and biological filtration to cultivate good things. - The advanced ceramic media is covered with thousands of porous pores, providing a large surface area for biological filtration and filtering out sparkling transparent water. - The medium block of the aquarium can effectively absorb fish waste and debris, and provide crystal clear water for the reproduction of fish. - Suitable for freshwater aquarium, planted aquarium, pool and pond. - Simple shape and look design, easy to place and use.