HTH 52040B Swimming Pool Care Shock Ultra, Swimming Pool Chemical, Cal Hypo Formula, 1lb (Pack of 6)The HTH All-One Shock Treatment is the ultimate solution for keeping your pool water crystal clear and sparkling. This powerhouse product increases chlorine levels, prevents bacteria, algae, stain, and scale, reduces skin and eye irritation, improves filtration, and softens your swimming pool water quickly and easily. Its Cal Hypo based formula sanitizes without adding cyanuric acid (CYA) to prevent overstabilization or chlorine lock, creating a visibly brilliant sparkle. The built-in visible blue action lets you know the product is working. Its compatible with all pool types, including vinyl-lined pools and saltwater systems. For best results, with HTH 6-Way Test Strips to test and balance your pool water twice weekly. Use weekly to solve 90% of pool problems within 24 hours and restore crystal clarity with HTH All-In-One Shock Treatment.