The Nature2 Mineral Spa Stick Sanitizer cartridges significantly reduces the need for bromine and chlorine while providing powerful sanitation for your spa or hot tub. Comes in a 3-pack. To easily maintain your spa or hot tub water, use a non-chlorine oxidizing shock while using the Nature2 Mineral Spa Stick Sanitizer. Available for spas up to 500 gallons, the mineral stick is placed in your spa filter cartridge and work with your existing system to provide you with the ultimate in hassle-free maintenance. These mineral sanitizer cartridges are EPA approved and use patented mineral bed technology to give you a fresh, clean spa without the irritating side effects of traditional chemicals. Nature2 Mineral Spa Cartridges last an average of four months.