Dr. marine 2PC Filter Sock NYLON 4" X 15.7" 200 micron Aquarium Filter Bags Two suture High Quality ,4 Inch Ring by 15.7 Inch Long Filter socks are the best form of mechanical filtration. This is an essential part for wet/dry filter systems, sumps, and diy filters. Removes excess food, detritus, organic wastes, and other particulates to lower ammonia levels and other undesirable substances. Used as mechanical filtration for any sumps and diy filters Quality: 2 Pieces