The Sta-Rite System3 D.E. filter incorporates the world’s finest filtration technology, which produces the ultimate in water quality. Diatomaceous earth (D.E.), a natural substance, is so fine it traps dirt and debris as small as five microns ( 1 ⁄ 10 the width of a human hair). That means body oils, suntan lotions, pollens, dust and even some bacteria are trapped in the filter, leaving behind sparkling clear, healthier water. That’s why this filtration process is recommended by professionals for hotels, resorts and health clubs.