Zodiac Nature2 G45 Replacement Cartridge Old P/N: W26745 New P/N: W28145 The Nature2 Professional G mineral sanitizer for in-ground pools delivers improved water clarity, and clean, safe water without the harsh effects of traditional chlorine-based treatments. Working with your pool filtration system, the Professional G uses elemental minerals that work with a small amount of chlorine to inhibit bacteria growth and eliminate contaminants. Minerals make the water noticeably softer, and less chlorine means no more red-eye, dry skin or foul odors. With Nature2 Professional G you get water that looks, feels and smells noticeably cleaner. Cartridge lasts 6 months