The HTH 4-in-1 Shock Treatment is a must-have for anyone who wants to keep their pool water crystal clear. This fast-dissolving formula kills bacteria and algae, reduces chlorine odor and irritation, and quickly restores crystal clarity. Its multi-functional shock treatment for weekly use can solve 90% of pool water problems within 24 hours. The Cal Hypo based formula sanitizes without adding cyanuric acid (CYA), preventing overstabilization or chlorine lock. Compatible with all swimming pools, including vinyl-lined pools and saltwater systems, this product is perfect for everyone. Use it with the HTH 6-Way Test Strips to test and balance your swimming pool water twice weekly for the best results. With HTH 4-in-1 Shock Treatment, you'll always stay all clear for cannonballs!