Aquatic Experts 4 inch Filter Sock 100 Micron Aquarium Filter Socks - 4 Inch Ring x 8 Inch Short Premium Felt Bags USA CUSTOM MADE: Our filter socks are constructed only when our US factory receives our exact specifications; years of testing produced the perfect blueprint. Other socks may look like ours but if you want the best you have found them. You will receive two 4 inch by 8 Inch felt filter socks with a 4-inch diameter plastic ring that will fit most sump holders. THESE DO NOT FIT RED SEA FILTERS. HIGH QUALITY AND REUSEABLE - Our aquarium felt filter bags or socks have interlocking fibers to trap floating debris, producing crystal clear aquarium water. Solid construction and heavy duty stitching make these socks STRONG AND DURABLE so they can be CAN BE CLEANED AND REUSED NUMEROUS TIMES. REMOVES FINE PARTICLES- Our 100 micron filter socks remove much smaller particles from water than 200 micron socks to produce polished, crystal clear aquarium water. Since they catch such tiny debris they will clog up faster than 200 micron filter socks. These felt filter socks are constructed with durable polypropylene which lasts longer than those made with polyester. SAFE FOR YOUR AQUATIC FRIENDS - Strict quality control ensures our filter socks remain aquarium-safe all the way from our USA manufacturer to you. You can now buy with confidence knowing that your filter socks will not come into contact with any harmful contaminants and will always arrive to your door safe for your aquatic friends. TIPS AND RISK-FREE GUARANTEE! You will receive our PROFESSIONAL CLEANING INSTRUCTIONS INCLUDED with your filter socks. In addition we are committed to our 100% CUSTOMER SATISFACTION so if you find that you are not 5-Star Happy with us or our products then please contact us and we will do whatever it takes to make sure you are 100% happy.