Aqua Kleen AK-5025 Unicel Replacement Filter Cartridge for Swimming Pool and Spa 60 sq. ft., 6 15/16" OD, Open Hole: 3 1/2" Top, Open Hole: 3 1/2" Bottom, 29 3/8" Long, AK-5025 Exact Fit for Unicel: C-6660 Exact Fit for Pleatco: PJ60-4 Exact Fit for Filbur: FC-1445 Guaranteed Perfect Fit - Extremely Durable - Wash & Reuse - Most Energy Efficient - Withstands High Pressures & Temperatures