Tier1 Replacement for ff-100 Freeflow Lagas FF-100 Pool and Spa Filter Cartridge COMPARABLE FIT: Length 6 5/8 inches, Outside Diameter 4 5/8 inches, Closed Top & 1 1/2 Inch NPT Bottom Hole. COMPARABLE REPLACEMENT: Freeflow Lagas, TLX and RLX. Pleatco PFF25TC-P4, Filbur FC-2400, Unicel 4CH-23. EXTREMELY DURABLE: High durable 3 ounce filter media HIGH QUALITY FILTRATION: High flow core designed to support the filter while providing industry leading flow rates 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.