Check the listing for details. Aquarium Filter Sock, SR Aquaristik 4” Replacement Nylon Filter Sock 200 Micron. Condition: New. Listed at 5.98 USD. SR Aquaristik 4” Replacement Filter Socks (Nylon) 200 Micron Easy to clean and reuse Fits most common sumps and holders Reinforced stitching for longer life SR Aquaristik Replacement Filter Socks are generally used in filter sumps, overflows or anywhere turbidity or debris needs to be removed from aquarium water. Using a filter sock reduces maintenance and increases the efficiency of chemical and biological filter media by removing small debris that can clog or be trapped. Felt filter socks are great for removing large amounts of debris but do not clog as quickly as nylon. Nylon filter socks generally need to be cleaned more often but are easier to clean. RETURN POLICY We want you to be happy with our products! If you are not 100% satisfied with your purchase, you may return it for a replacement or a refund of the full product cost within 30 days. It's part of our no-risk customer guarantee! (please see the details under the Shipping & Payments tab)