This Replacement filter cartridge replaces Unicel # C-4301, Pleatco # PMT27.5 and Filbur # FC1616 and meets OEM # 221022 specifications. This 14 7/8 inch long and 4 15/16 inch wide filter cartridge can handle the top load of 28 square feet and is the best fit for Martec, Sonfarrel, Advantage Spa. This high quality filter cartridge gives you pure water free from germs and sand for pools and spas. Very easy to install this filter cartridge is made of superior grade of materials.