Guardian pool/spa filter fits:Pleatco: PFF50P4 | Unicel: 5CH-45 | Filbur: FC-2401freeflo,freeflow, aquaterra spas
Single filter replacement: Pleatco: PFF50P4 | Unicel: 5CH-45 | Filbur: FC-2401 Diameter: 5 5/16" Length: 10" Top: Open Hole: 2 1/8" Bottom: 1 1/2" MPT Threaded Filter Area: 45 sq ft Filter Material: reemay (3 oz/yard)