Cal Shock Contains 68% active ingredient.Convenient, easy to use & fast dissolving. Economical.Effective Sanitizer - The available chlorine (65%) is released when the product is dissolved in water and it works continually to prevent growth of algae & bacteria.Shock treatment – Used for shocking or super chlorinating pool water to destroy organic contaminants and clear up hazy water. Shock treatment – Used for shocking or super chlorinating pool water to destroy organic contaminants and clear up hazy water Easy to use Clears up hazy water and helps prevent algae growth Works continually to kill bacteria Granular 68% Calcium Hypochlorite