The Filter Frog conveniently fits inside your hot tub?s filter cartridge, providing FROG mineral protection for hot tubs up to 600 gallons. Supplement with a low level of chlorine or bromine and hot tub care is complete with soft water and a crystal clear shine. Filter FROG simply fits into the center of a spa filter cartridge. It is a one piece design that can be shortened if necessary. The water moves in and out of the louvered design, dispensing a low level of minerals into the spa. Simply supplement with 1 ppm of chlorine or bromine. Only one other company has a similar product using silver to destroy bacteria. Their product requires a period of shocking the hot tub to activate the minerals, while FROG minerals are active immediately. They also supplement with non-chlorine shock, which means there is no safeguard of a low chlorine or bromine residual in the water to protect the bathers. With Filter FROG, you can count on it.