These C3 8oz 3" Chlorine tablets are made from 99% Trichloro-S-Triazinetrione and 90% Available Chlorine. Made with the most concentrated form of dry chlorine. They are consistent in size and dissolve slowly, so you can reliably dose the pool once a week. These tablets contain cyanuric acid, a stabilizer that prevents ultraviolet light from removing the available chlorine from your pool. With these tablets, you can easily maintain the right chlorine balance and produce beautiful, clean sparkling water effortlessly. Simply add tabs to chlorine floater or chlorinator, 1 tablet treats 10,000 gallons of water. For best results, we recommend testing the chlorine level once per week and maintaining proper pool water balance.??