This is the PERFECT combination of a water container/bottle and filter. After all, LifeStraw is the leader in emergency, portable water filters, but who wants to have to stick their face in that little puddle or stream to get a drink thru the straw all the time. With this little accessory you just fill up the collapsible bottle, screw on the filter and cap and you have clean filtered water without laying on the ground. And it's so lightweight that packing it empty is no problem at all. Takes up no room at all in your pack and weighs NOTHING. I bought 2, one for me AND the wife.