A main stay for travelers around the world, who want water suitable for drinking. The iodine tablets kill viruses, bacteria and giardia without the weight, cost and bulk of a water filter.Includes 50 tablet; 2 tablets will treat 1 quart of water. Each tablet contains 20mg of tetraglycine hydroperiodide, which releases 8ppm of titratable iodine. Potable Aqua tablets require that you waitw at least 30 min, before drinking the treated water. Unopened bottles of Potable Aqua should remain effective up to 4 years under controlled temperatures between 60 and 86 F. Caution:Iodine tablets are not effective against Crytospordium. An opened bottle of Potable Aqua should not be kept for more than one year.