For use with spa frog floating and in-line systems. When the mineral cartridge is used on setting 6 the cartridge will last 4 months.The item “4 Spa Frog Mineral Cartridges (FOUR)” is in sale since Wednesday, May 06, 2015. This item is in the category “Home & Garden\Yard, Garden & Outdoor Living\Pools & Spas\Spas & Hot Tubs”. The seller is “mman3229″ and is located in Yonkers, New York. This item can be shipped to United States.