Hotspring Hot Tub 3 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 traditional 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 is visibly clearer and more pleasant to the senses. Easy to install and requires minimal maintenance. Compatible with most spa maintenance systems. The mineral filter stick offers 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. Effective for continuous 24-hour water treatment.