Skimmer tabs that make pool water sparkle. Slow dissolving but fast acting. Lasts for up to one week. Softens water. Does not contribute to the build-up of stabilizer that makes chlorine less effective. Does not contain Cyanuric acid. Destroy bacteria and algae and get a visibly brilliant sparkle that lasts. Traditional chlorine products contain cyanuric acid (CYA). When too much CYA builds up, it can cause overstabilization or chlorine lock, cloud your water and cause algae growth. The slow-dissolving Cal Hypo formula in HTH Chlorine Skimmer Tabs provides a steady source of available chlorine without adding extra (CYA) for beautifully clear water. This product is great for all pool types including vinyl-lined pools and salt water systems.