Nature2 SwimPure Mineral Cartridge N2CW25 N2C900 N2C1200 N2C1750 Reduce chlorine usage up to 80%. Lasts 6 full months. Replaces N2CW25 N2C900 N2C1200 N2C1750 For use in pools up to 25,000 gallons Star-Clear/Star-Clear Plus C751/C800/C900/C1100/C1200/C1500/C17502