Genuine Freshwater Salt Cartridge for hot tubs supporting Freshwater Salt Systems Compatible with all Hot Springs Limelight, Highlife, and Caldera Paradise and Utopia lines of spas Our freshwater salt box is a product born out of market research and customer needs. It lasts up to 4 months with minimal maintenance. It can be used with your existing filter. Simply place your hot tub stick into the filter and you can enjoy 4 months of worry-free spa experience! Makes the water filtration of your hot tub more thorough, ensuring your spa time is more comfortable, warm, and provides the best spa service you expect, and even more.