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.