Make questionable water drinkable with Chlorine Dioxide tablets that kill bacteria, viruses and cysts, including Giardia and Chryptosporidium. Enjoy your favorite outdoor activity or be safe when traveling in a foreign country knowing nearly 100% of the most common and serious water contaminants will be killed within hours of treatment. When used properly the product leaves no unusual aftertaste. One tablet per quart of water, 4 hours ahead for best results. 20 tablets per bottle.