Pack of 4 premium quality professional grade aquarium and pond felt filter socks that are 14 inches long and have 4-inch plastic rings that will fit most overflow sump systems and holders. 200-micron socks that instantly improve the water quality without clogging too quickly.Premium reusable felt filtration socks with heavy-duty stitching that are strong, durable, and have been constructed to be cleaned and reused numerous times without breaking down. Filter socks are great for freshwater and saltwater aquariums, koi ponds, reefs, terrariums, etc.These premium 200-micron felt filter socks have interlocking microfibers that provide exceptional mechanical water filtration, so they are ideal for trapping smaller organic matter, uneaten food, excreted waste, decaying plants, and other debris. This excellent filtration ensures that your aquarium water always stays crystal clear.Always clean or change your filter sock regularly to maintain a high water quality standard, which keeps your aquatic animals happy! Regular filter sock changes will remove the solid organic matter before it has a chance to breakdown, and bring on the growth of algae growth or ammonia buildup.Master Pet Supply is a trusted supplier to the pet industry, so purchase our products with the confidence that we'll offer you a 100% lifetime satisfaction guarantee that if you're not happy with them at any time, we'll provide a full replacement or refund.