BioGuard Burnout 73 is a superchlorinator for swimming pools. With the highest percentage of calcium hypochlorite of all the BioGuard shocks this one bag treats 16,500 gallons of water making it one of the strongest shocks on the market. 73% Calcium Hypochlorite Reduces Organic Contamination Increasers Water Clarity Destroys Organic Contaminates Restores Sparkle and Clarity to Swimming Pool Water Quick Desolving For use with all swimming pool surfaces