Katadyn Micropur MP1 Purification Tablets (20 Tablets) The only tablet or liquid proven effective against viruses, bacteria, Giardia, and Cryptosporidium in all water conditions Works in 30 minutes in most water (four hours if the water is cold and dirty) The only purification tablet (or liquid) EPA registered as a microbiological water purifier Each tablet is premeasured to treat one liter of water; no mixing or measuring required Tablets are individually sealed in waterproof strips for a longer shelf life and to reduce weight