Hayward D.E. Perflex Extended Cycle Pool Filter, 40 sqft, 80 GPM W3EC75A Perflex Extended-Cycle D.E. filters clean pools fast, removing particles as small as two microns the first time through. Its patented Flex-Tube™ design gives longer cycles between cleaning because the same D.E. filter powder is used over and over. Plus, Perflex cleans without backwashing, saving hundreds of gallons of treated pool water. An exceptional value as a replacement filter or for new pool installations.