Ready to use media bags, convenient use for all types of aquarium filters. Good to use in both fresh and saltwater tank. Hollow shape enhances biological filtration capacity allowing water flow through and less likely to get clogged. Porous ceramic material offers efficient biological filtration and maintains a healthy aquatic environment. Ceramic rings size: 1/2"x 1/2". Mesh bag size: 8"x 5.5". The mesh bag is reusable, and the zipper is made of plastic. Package includes: 6 lbs premier bio ceramic rings in 6 mesh bags Brand: AQUAPAPA These Bio Ceramic Rings are good for all types of filters. Its cylindrical and hollow shape allows water flow through and less likely to get clogged.