Lifesystems\' Chlorine Dioxide Tablets will treat up to 30 litres of water, and has been found to be the most effective form of chemical water disinfection. It doesn\'t have any after taste or harmful byproducts, but still protects your gut from bacteria, viruses and cysts found in water while travelling and hiking (Including Giardia and Cryptosporidium). 30 foil sealed tablets treats up to 30 litres of waterWeight: 40gOnce opened use within 18 months Safe for long term useDoes not leave any residual taste, odour or colour