Ensure that your swimming pool water stays crystal clear with these 8 filters. The Purex Replacement Vertical DE Swimming Pool Filter Grids are compatible with Pentair Purex 2000 series D.E. filters and Pentair Purex 4000 series D.E. filters. D.E. or diatomaceous earth filters are ideal for the cleanest, most sparkling pool and spa waters because they can trap debris as small as 2 to 5 microns. For perspective, a human hair measures between 30 and 120 microns. That's why many in the industry call these filters "water polishers."The diatomaceous earth filter grids can be cleaned and recoated with D.E. powder to lengthen their life, but at some point, they become too worn or damaged to be effective with a life expectancy between 2 to 3 years. These replacement filters are made of spun-bonded, 100 percent polyester materials and will require cleaning less often than other filter grids. Spend less time cleaning your pool and more time enjoying the freshwater with the 8 pack of Replacement Vertical Pool Filter Grids from Unicel.