Hotspring Hotub 3 Spa Mineral Ion Cartridge Filter Sticks For Hot Tub- Spa Mineral Ion Cartridge Filter Sticks For Hot Tub(3, Grey) Minerals ion cartridge brings you clean and crystal clear spa water without high levels of heavy chemicals.Active ingredient is zinc.(inert ingredients are vitamin c,calcium sulfate,zeolite,attapulgite-type clay,zinc oxide and magnesium oxide.)A difference you can see,smell and feel,spa mineral cartridge improves water quality.Easy to install and low maintenance,compatible with most spa maintenance products.Mineral filter stick is a uncomplicated option for you,enjoy your relaxing spa experience with a mind at ease.Controlled mineral ion release technology, automatically dissolving trace amounts of mineral elements into the water.Mineral Stick works with existing filtration system,designed to fit most spa and hot tubs filters,available for 24 hours flow."