Purchased brand new and never used. Expires 12/2026. One pack of 20 Potable Aqua Chlorine Dioxide Water Purification Tablets Effective against bacteria, viruses and cysts, such as Giardia lamblia and Cryptosporidium Emergency water purification for camping, hiking, traveling and emergency preparedness situations Add one of these water purifying tablets to one quart (one liter) of water and allow 4 hours for treatment Water bottle purifying tablets with 2.6 times the oxidizing capacity of chlorine.