6 Guardian Pool Spa Filter Replaces Unicel C-4401 C4401 4401 PLEATCO PRB17.5Sf Fc2386 Outside Diameter: 4 - 15/16" (4 15/16") Length: 4 - 5/8" (4 5/8") Top Opening: 2 - 1/8" (2 1/8") Bottom Opening: 2 - 1/8" (2 1/8") Media Weight - 3 oz. SQ FT Media - 35' Unicel - C-4401 C4401 Filbur - FC-2386 FC2386 Pleatco - PRB17.5SF