Aqua Kleen AK-3009 Unicel Replacement Filter Cartridge for Swimming Pool and Spa 25 sq. ft., 4 5/8" OD, molded cone handle Top, Open Hole: 1 9/10" Bottom, 9 3/4" Long, AK-3009 Exact Fit for Unicel: C-4324, 4CH-24(MPT) Exact Fit for Pleatco: PGS25 Exact Fit for Filbur: FC-0187 Guaranteed Perfect Fit - Extremely Durable - Wash & Reuse - Most Energy Efficient - Withstands High Pressures & Temperatures