Sohler 1 LB Bio Ceramic Rings Aquarium Filter Media in 1 Free Mesh Bags Biological filtration media that helps remove harmful ammonia and nitrite in the water Ready to use bags, convenient use for all types of filters. Good to use in both fresh and saltwater tank The ceramic material that the ceramic rings is made of is porous. The tiny pores make it an ideal home for beneficial bacteria to grow. Mesh bag size: 8"x 5.5". The zipper-designed bag is reusable. Ceramic rings size: 1/2"x 1/2" Package includes: 1 lb premier bio ceramic rings in mesh bag