On my recent trip to Sri Lanka, I decided to pack even lighter than usual. Of course, I never check luggage -- even when traveling internationally for 6+ weeks. But, this time, I wanted to minimize the number of bulky items I packed because I planned to stow my soft luggage under my seat rather than in the overhead compartment. Aside from one extra pair of shoes, the bulkiest item was my special water bottle that is a water filter. So, instead of traveling with the Lifestraw Go bottle, I purchased the Katadyn BeFree which is a soft, collapsible, BPA-free flask. It comes in three sizes: a little over half a liter, as well as one liter and three liter models. (I picked the half liter model for my travels.) Weighing in at just two ounces and packing relatively small, this was ideal for my journey. You simply suck from the spout and the filter removes 99.9% of protozoa and 99.9999% of bacteria from the water (It doesn't remove viruses.) And, when you unscrew the spout, the wide mouth of the flask makes it easy to fill from the faucet.