Chlorine granules that provide visible sparkle and crystal clear water in just 24 hours. 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 Cal Hypo based formula in HTH Chlorine Granules Ultra provides chlorination without adding extra CYA for beautifully clear water all season. The all-in-1 action also kills bacteria and algae, clarifies and softens pool water, prevents stain and scale, and provides a filter aid for the ultimate convenience in DIY pool care. This product is great for all pool types including vinyl-lined pools and salt water systems.