NEW Pair of NATURE 2 W28125 Mineral Cartridges. These Pool Purifier Cartridges destroy bacteria and control algae using natural minerals. Reduces potential for stinging eyes, skin irritation, and unpleasant odors; helps stabilize pH levels. The cartridges can be used for 10.000 - 25.000 Gallon Pools and will last up to 6 months.