Crystal Clear Aquatics AAD00283 150-Micron Polypropylene Media Bag with Draw String, 8-Inch by 4-Inch This 150 micron mesh bag with built-in drawstring is used to hold media in aquariums and ponds Made of polypropylene material It is industrial grade, machine washable and re-usable Can be used with any media including all types of carbon, ammonia, nitrate and phosphate reducers Measures 8-inch length by 4-inch width