DuoClear® Cartridge, 4/Pack is designed for the Nature 2 DuoClear® chlorination system, and sanitizes pools between 35,000 and 45,000 gallons. Its mineral bed technology integrates silver and copper to maintain a healthier swimming pool. It is designed to produce low levels of chlorine that combine with mineral activity for soft and silky water. The DuoClear® 45 cartridge boasts a six-month lifespan, providing purer pool water with reduced chemical use for an entire swim season.