Guardian Pool/Spa Filter &bull; Replaces Watkins Hot Springs, Unicel C-6430, Pleatco PWK30, Filbur FC-3915 Outside Diameter: 5 - 7/8" (5 7/8") Length: 10 - 1/2" (10 1/2") Top Opening: 1 - 15/16" (1 15/16") Bottom Opening: 1 - 15/16" (1 15/16") Media Weight - 3 oz.