BioGuard Arctic Blue Shock is the perfect first step in winterizing your pool, killing off bacteria, algae, and other contaminants that can wreak havoc on your pool during the long winter months. Its powerful granular formula can be quickly broadcast into your pool without needing dilution, saving you from handling messy liquids. When used in conjunction with an effective algaecide, your pool will stay clean and healthy throughout its winter slumber, making spring openings much faster and hassle-free. Best of all, Arctic Blue Shock is made right here in the USA to ensure the highest quality, allowing you to buy with confidence.