The Unicel Swimming Pool Filter is made from heavy-duty polyester and is designed to last far longer than cheaper alternatives while having more pleats to improve filtering capacity. Note: 50 sq. ft. C 4950 is an upgrade to 25 sq. ft. C 4326 and C 4625 cartridges. Unicel replacement filter grids are recognized as the best grid replacements in the industry. They have received numerous awards year after year for their performance and quality of products. We are an Authorized Unicel Dealer. An appropriate cleaning schedule will both help the performance of the filter and keep it from breaking for longer periods of time. However, it is not a permanent part and standard use will result in the need for a replacement. Make sure you go with the highest quality standard of replacement: Unicel.