Tier1 PTS35 Thermo Spas FL1009, Thermo Spas Healing Spa, Pleatco PTS35, Filbur FC-0187, Unicel C-4324 Comparable Replacement Filter Cartridge AFFORDABLE REPLACEMENT: Replaces cartridges Pleatco PTS35, Filbur FC-0187, Uncel C-4324 INCREDIBLY SIMPLE TO USE: Easily replaces the old filter cartridge with 35 Sq. ft. media EXTREMELY DURABLE: Measures 9 3/4 inches (length) x 4 3/4 inches (outside diameter); Top Handle and Bottom 1 7/8 Inch Diameter FITS THE MODEL NUMBERS: Thermo Spas Healing Spa 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.