Waterway, Rainbow, CMP, Hydro, Nahani by Maax

The Unicel C-4975 hot tub filter has the 2-1/8 inch holes on the top and bottom and is 20-1/8 inches long with a 4-15/16 (5) inches diameter. For optimal fit and performance, verify that this filter cartridge matches the dimensions of the old filter in your spa. Filter details: Unicel P/N: C-4975 Diameter: 4-15/16" Length: 20-1/8" Top: 2-1/8" Open Bottom: 2-1/8" Open Media: 75 sq.ft. Filter Media: 3oz Reemay Pleat count: 210 Compatible replacement for: Pleatco PRB75 Filbur FC-2395 Pentair 17-2632 Rainbow RTL-75 CMP 25390 Pentair R173435 How long should Unicel hot tub filters last? While most hot tub filters need to be changed every six to twelve months, Unicel brand filters are made with REEMAY premium trilobal filtration media that delivers 45% more surface area over standard rounded filter fibres and can last up to 18 months or more, depending on your level of hot tub use and filter cleaning routine.