Aqua Kleen AK-4007 Unicel Replacement Filter Cartridge for Swimming Pool and Spa 50 sq. ft., 5 7/8" OD, semi circular handle Top, male slip fitting w/ molded o ring Bottom, 12 3/4" Long, AK-4007 Exact Fit for Unicel: C-5350 Exact Fit for Pleatco: PLW50-4 Exact Fit for Filbur: FC-3101 Guaranteed Perfect Fit - Extremely Durable - Wash & Reuse - Most Energy Efficient - Withstands High Pressures & Temperatures