A stabilized form of chlorine (chlorinated isocyanurate) usually sold in tablet or stick form for use in automatic chlorinators or in floating dispensers since it is very slow dissolving. It has a very low pH and will lower pH and TA. It will cause CYA levels to rise with continued use so it is not a good choice for those with cartridge filters or in climates that do not winterize pools and have an extended swim season. It will add .6 part CYA for every 1 part of chlorine it adds.