Spa Mineral Ion Cartridge Filter Sticks for Hot Tub (3, Grey) Minerals ion cartridge helps maintain clean and clear spa water with reduced reliance on traditional chemicals. The active ingredient is zinc. Inert ingredients include vitamin C, calcium sulfate, zeolite, attapulgite-type clay, zinc oxide, and magnesium oxide. Experience improved water quality that is visible, odor-free, and pleasant to the touch. Easy to install and requires minimal maintenance. Compatible with most spa maintenance systems. Designed for simple integration with existing filtration systems, this mineral stick fits most spa and hot tub filters. Features controlled mineral ion release technology that gradually dissolves trace minerals into the water. Works continuously for 24 hours of flow.