DuoClear® Cartridge, 35 gals Bulk 4/Pack sanitizes pools between 25,000 and 35,000 gallons. Its mineral bed technology integrates silver and copper to maintain a healthier swimming pool. The Nature2® DuoClear® , Fusion, and Fusion Soft systems are designed to produce low levels of chlorine that combine with mineral sanitation for soft and silky water. Using the Zodiac Nature2® DuoClear® , Fusion, and Fusion Soft systems will help reduce chemical use by up to 50% and less overall pool maintenance. It controls bacteria and algae to provide a clean and safe swimming experience. The DuoClear® 35 cartridge boasts a six month lifespan, providing purer pool water with reduced chemical use for an entire swim season.