This replacement filter cartridge replaces Unicel # C-4637, Pleatco # PRB37-IN-4 and Filbur # FC-2380 while it complies with OEM # C4637 specifications. It is capable of handling the top load of 35 square feet and the most suitable for Rec Warehouse, Rainbow, Waterway Plastics, Morgan Spa, Leisure bay mfg, Lifestyle Spas, Infinity Spas by Maax, Pentair Pool , Statewood spas, Savannah spas, Freedom Spas, Acryx-Maax Spas (Canada). By installing this filter you get clean and clear water for your pools and spas free from germs and spas.