?Spa mineral stick for hot tubs up to 500 Gallons/2000L,hot tub mineral sticks serve your hot tub with low maintenance. ?KOROWA spa mineral stick significantly improves look & feel of water,improves performance of spas,bring you crystal clear water. ?Alternative to heavy chemicals,spa mineral sticks for reduces hot tub bromine and chlorine usage by up to 50% in most spas, without high levels of chlorine or bromine-low maintenance,You can now enjoy Spa and hot tub experience with healthier pH levels. ?Low maintenance and low cost with a duration up to 4 months,easy to install and simplifies water balance,hot tub mineral sticks unaffected by heat,works with your existing flow rates Installation,Just Simply drop the stick into your existing filter and let the mineral sticks do their work. ?Compatible with most spa maintenance products & designed to fit most spas and hot tubs;compatible with most suction-side and pressure-see filters. BUT ATTENTION PLEASE: KOROWA HOT TUB SPA MINERAL STICKS MINIMUM REQUIRED FILTER LENGTH IS APPROX 7",MINIMUM FILTER HOLE DIAMETER IS 1-1/4"!!!