A few years ago, I watched a demonstration by the boss of Water-to-Go whereby he put dirty river water into a reusable plastic bottle with a replaceable filter and then filtered that water into a glass. The water was now crystal clear and he drank it. With all the demos he did that day, I did not actually check to see how close he was to the Gents! I bought two of the bottles and they have been used on every trip since to India, Myanmar, Thailand, Russia, Mongolia, Papua New Guinea, Rwanda, South Africa and Jordan.