Aqua Kleen AK-6057 Unicel Replacement Filter Cartridge for Swimming Pool and Spa 100 sq. ft., 7 1/4" OD, Open Hole: 3 1/16" Top, Open Hole: 3 1/16" Bottom, 29 1/2" Long, AK-6057 Exact Fit for Unicel: C-7497 Exact Fit for Pleatco: PJAN100 Exact Fit for Filbur: FC-5180 Guaranteed Perfect Fit - Extremely Durable - Wash & Reuse - Most Energy Efficient - Withstands High Pressures & Temperatures