With the BeFree(TM) AC Filter, you no longer have to worry about where your next drink will come from. Just fill up the flask and let the EZ-Clean Membrane(TM) do the work. Gently squeeze the flask for instant refreshment. Maintain the EZ-Clean Membrane quickly and easily for longer life and more enjoyment by simply filling the flask with water, attach the cover and shake the debris free. Or, remove the filter from the flask and swish in any lake, river or stream. When you're ready to "hit the road", the flexible flask collapses down to fit into tight spaces. Just smash, stash and go! Worry less, discover more, BeFree!