One tablet purifies one liter of water. Great for travel, camping and rafting trips or as an alternative to a water filter. No aftertaste - improves the taste of odor of treated water. The only tablet that is EPA registered as a water PURIFIER. Meets EPA microbiological water purifier test standards. Lighter to carry than all water filter designs. Effectively kills bacteria, Giardia, Cryptosporidium, viruses and cysts in contaminated water. Easy-to-use tablets. 30 tablets.