Velishy(TM) Fish Tank Aquarium Marine Sump Felt Filter Bag Material: Polypropylene, Color: White Micron rating: 150 micron (0.15mm) / 200 micron (0.2mm) Ring width:Approx 4 inches, Length: Approx 15 inches 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 Package included:1x Aquarium Filter Socks