HTH Pool Care Shock Ultra is an advanced pool shock that makes weekly upkeep simple and certain. This all-in-1 Cal-hypo swimming pool shock treatment boosts chlorine fast, fights bacteria and algae, and helps reduce eye and skin irritation without adding cyanuric acid (CYA) that can lead to chlorine lock. It also helps prevent stain and scale, improves filtration, and softens water for a visibly brilliant sparkle within 24 hours. Safe for vinyl liners and ideal for all pool types, this dependable pool shock treatment keeps your routine strong and your water confidently clear.