Guardian Spa Filter Replaces Unicel 4CH-23 Pleatco PFF25TC-P4 Filbur FC-2400 Free Flo Spas Replaces Pleatco: PFF25TC-P4 | Unicel: 4CH-23 | Filbur: FC-2400 Diameter: 4-5/8", Length: 6-5/8", Top: Closed, Bottom: 1-1/2" MPT Threaded Filter Area: 19 sq ft Used in Freeflo Spas