Pura Media Bags are designed for professional filtration applications. Features 300-micron mesh, keeps media in preventing fines from washing out of the bag. Self fastening closure is far superior to drawstrings and provides an additional leak proof safety factor. The bags are washable, reusable and completely safe for both fresh and saltwater aquariums. Provides extra versatility, neatly folds over and will fit many of your specific applications. Easy to use, just fill the bag with your media of choice and pinch self fastener to close. Ideal for phosphate removing media, ion exchange resins, carbon, zeo-sorbents, peat and bio-medias. Measures 6-inch length by 12-inch width. Includes 3 bags per pack.