HWD EC50 25sqft Perflex Above Ground DE Filter Hayward Perflex D.E. filters provide the deepest, most comprehensive clean, removing microscopic dust and pollen as small as one micron 100 times smaller than a grain of salt. Providing crystal clear, sparkling water at an economical price, it the Perflex D.E. Filters have been proven reliability, and energy savings over many years, Perflex has set the standard in swimming pool filtration by incorporating the patented Flex-Tube™ design in combination with D.E. filter powder the most efficient dirt remover known for pool filtration. The result is superior water clarity, extended filter cleaning cycles and no backwashing required. Captures all dirt, removing microscopic dust and pollen as small as one micron Traps algae Efficient one-pass cleaning power No Backwashing "bumping" activates Flex Tubes™ repositioning dirt and D.E. within the filter