Sumpsock Aquarium Filter Bags, Filter Socks, Extra Thick Felt, Reusable, Made in The USA 200 Micron sock with 4" plastic ring, 14" long, welded seams for strength Removes excess food, detritus, organic wastes, and other undesirable substances. Filter socks are the best form of mechanical filtration for sumps and DIY filters Using these filter socks will improve your aquarium's water clarity and quality. Can be cleaned and reused numerous times.