Jack's Magic 02 Safe Shock - Stain Solution #3 gives pool owners a way to shock their pool without adding chlorine, making it perfect for ozone, ionization and biguanide-sanitized pools. Its unique formula is neither chlorine nor monopersulfate (MPS) based, and introduces 12% more active oxygen than competing MPS shocks. This makes it more effective at killing off bacteria and other organic compounds from your pool, and can even be used as a pre-treatment for acid washing your pool free of copper stains. Best of all, Stain Solution #3 is made by Jack's Magic, an industry innovator in pool and spa chemicals for years, allowing you to buy with confidence.