Hayward W3EC40AC Perflex 20 sq.ft. Modular Filter with ClampEnjoy cleaner, clearer water with the Perflex 20 sq ft Modular D. E. Filter with Clamp. Shasta Pool Supply markets the best prices on Hayward above ground pool equipment. Specifically, the W3EC40AC Extended Cycle technology reduces the need for frequent maintenance and captures even the finest particles down to 2 microns. 20 sq ft Filtration Capacity Patented Flex Tube Design Easy Clamp Assembly Eco Friendly Filtration