Nature 2 Spa Cartridge for Spas up to 1000 Gallons Manufacturer ZODIAC NORTH AMERICA POOL CARE Manufacturer Number W20660 Price: $45.99 Quantity: 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 Description Nature2 is a water purifying system which uses trace elements to maintain a more balanced spa. Using Nature2 allows you to use significantly less harsh chemicals. The silver in Nature2 combined with chlorine assists in maintaining the sanitation of the spa. Nature2 keeps spa water stable even in hot weather. Lasts 4 months, for spas up to 1000 gallons