Tier1 Replacement for Dynamic 17-2327, Pleatco PRB25-IN, 817-2500, R173429, Unicel C-4326, Filbur FC-2375 Spa Filter Cartridge AFFORDABLE REPLACEMENT: Replacement Pleatco PRB25-in Spa filter for 25 sq ft Spas, Dynamic Series systems, and any Spa systems that need 5 inch (Outside diameter) by 13 5/16 inch (Length) filters. INCREDIBLY SIMPLE TO USE: Easily replace your old Unicel C-4326, FC-2375, PRB25-in Spa Filter with the Tier1 17-2327 Spa filter. EXTREMELY DURABLE: Durable and Washable Pleated fabric that maintains strength even when loaded with sediment, our high flow core is designed to support the filter while providing industry leading flow rates while causing less wear and tear on your pump. SPA FILTER CARTRIDGE REPLACEMENT: This Tier1 Dynamic RDC-25 filter can be used in place of your C-4326 Spa filter. 100% TIER1 NO WORRIES GUARANTEE: We stand behind the quality of filtration and overall performance of our Tier1 filters! Replace your filter when the pressure gauge on your filter tank reaches 8 psi above the pressure recorded when first installed. Turn off the power to your pump and bleed the excess air pressure of the system using the air valve on the filter. Remove any band clamps and/or lids to your filter. Remove the cartridge from the filter canister and dislodge any loose debris Rinse the cartridge thoroughly with clean fresh water and return it to the filter tank. Secure the tank lid and any band clamps.