Since I travel internationally a lot, I wanted a filtered solution for my bottle - the Grayl seems to be the best in that regard, works similar to a french press - separate the 2 parts, fill, press and done. The only issues might be that it's not collapsible in any way and sometimes TSA sees the filter as water in the bottle - I have to tell them it's a filter and the bottle is really empty. Once I had to unscrew the cap and turn it upside down with my hand under to prove my point. I've never gotten sick from water issues when traveling with this, I can filter water and use that to fill a different bottle if I need to as well. (Or pour it in a glass to use to brush my teeth, etc.) You can't do that with those sip and filter type bottles.. My personal bag has a water bottle sleeve on one end it fits nicely into, and while in flight I put it in the seat pocket. (Just remember to slightly crack open the cap or it will start to drool a bit from where the 2 pieces come together when the air pressure changes....) Not the cheapest solution by far, but I love the peace of mind.