Potable Aqua Germicidal Water Purifier Tablets are essential for any outdoor adventurer. These water treatment tablets make questionable water bacteriologically suitable to drink, even in emergency water purification situations. Add 2 water purification tablets for drinking water to 1 quart (1 liter) of water and cap loosely to allow a small amount of leakage. After 5 minutes, shake container to allow screw threads to be moistened, then tighten cap. Allow 30 minutes for water purifying tablets to disinfect water for safe drinking. These backpacking water purification tablets are effective against Giardia lamblia when used as directed. When it comes to water safety and emergency preparedness, Potable Aqua is the most trusted name in water purification tabs and products. Use portable water purifier tablets for travel as directed on the label.