RING STYLE – FITS STANDARD FILTER CUPS: These felt aquarium filter socks feature a smooth molded plastic ring designed to fit standard filter cups and holders commonly used in sump systems, and they are not compatible with Red Sea filter trays. 200 MICRON FELT FOR MECHANICAL FILTRATION: Made from dense polyester felt, these sump filter socks provide reliable mechanical filtration by capturing fine particles such as uneaten food, fish waste, detritus, and debris. DURABLE, REUSABLE CONSTRUCTION: Heavy duty felt material maintains its shape and filtration performance through multiple cleanings, offering a long lasting filter media option trusted by aquarium owners and service professionals. IMPROVES WATER CLARITY: Interlocking micro denier fibers trap suspended particles before they break down, helping maintain cleaner, clearer water in both saltwater and freshwater aquariums. EASY MAINTENANCE: These filter socks can be cleaned and reused multiple times, and regularly replacing or cleaning them supports strong mechanical filtration and consistent sump performance. These Aquatic Experts Ring Filter Socks are designed for reliable mechanical filtration in sump based aquarium systems. Each aquarium filter sock is made from dense polyester felt and features a smooth molded plastic ring that fits standard filter cups and holders for a secure, consistent fit. The felt material provides dependable 200 micron mechanical filtration by capturing fine particles such as uneaten food, fish waste, detritus, and suspended debris, helping maintain cleaner and clearer water in both saltwater and freshwater aquariums. Built for long term use, these sump filter socks maintain their shape and filtration performance through multiple cleanings, making them a trusted choice for aquarium owners and service professionals. The interlocking micro denier fibers offer strong particle capture without restricting flow, supporting efficient sump operation as part of your regular maintenance routine. These socks are not compatible with Red Sea filter trays. Whether used in reef tanks, fish only systems, or mixed aquarium setups, these felt filter socks provide a simple and effective filter media solution to enhance water clarity and support consistent mechanical filtration.