The Frog @Ease SmartChlor Cartridge for Swim Spas is an integral part of the Frog @Ease Floating Sanitizing System. When applied to the mineral cartridge, they combine to create an efficient and constant supply of chlorine and minerals to ensure a soft and safe swim spa environment. This cartridge is intended to be replaced every 3-4 weeks, or if the spa needs to be drained and refilled. Using this product eliminates the hassle of consistently adding chlorine treatments to the water without sacrificing sanitized water.