The recommended once-a-month non-chlorine maintenance shock for swim spas. Cut open, pour in, and 15 minutes later your swim spa is clean, clear and ready for you! Helps extend the life of the FROG @ease SmartChlor Cartridge for Swim Spas. And definitely extends easy swim spa water care for you! It’s Cyanuric Acid free. No mess, no guess, no stress swim spa water care maintenance at your fingertips!