Spa Mineral Ion Cartridge Filter Sticks for Hot Tub (3, Grey) Mineral ion cartridge helps maintain clean and clear spa water with reduced reliance on heavy chemicals. Active ingredient is zinc. Inert ingredients include vitamin C, calcium sulfate, zeolite, attapulgite-type clay, zinc oxide, and magnesium oxide. Enjoy improved water quality that you can see, smell, and feel. Easy to install and low maintenance, compatible with most spa maintenance programs. The mineral filter stick provides a simple solution for enhancing your spa experience. Features controlled mineral ion release technology that gradually dissolves trace minerals into the water. Designed to work with existing filtration systems and fits most spa and hot tub filters. Suitable for continuous 24-hour flow.