For Inground or Aboveground Swimming Pools Reduces eye and skin irritation Easy to replace cartridge Destroys bacteria Capacity: 5,000 - 25,000 Gallons Pools The Nature2 W28175 Express cartridge allows pool owners to bring all the benefits of mineral technology to their existing pool. During the regular pool filtration cycle, water flows through the Nature2 W28175 Express cartridge, where a combination of silver and copper minerals destroy bacteria. This process significantly reduces the need for large amounts of chlorine, limiting the potential for eye irritation and unpleasant odors. Cartridge lasts 6 months. Run Time: 6 Hours a day minimum. Cleaner, clearer, softer water with less chlorine. Better for the Environment.