This Replacement filter cartridge replaces Unicel # C-4970, Pleatco # PCAL75 and Filbur # FC-2930 while it complies with OEM # 817-7500 specifications. This 23 5/8 inch long and 4 15/16 inch wide filter cartridge is capable of handling the top load of 75 square feet and is best fit for Waterway Plastics, Leisure Bay Spas, Sunbelt Spas. It has 2 1/8 inch open holes both at the top as well as bottom. You get clean and clear water in your pools and spas by installing this filter cartridge which is very easy to install and made of high quality of materials.