Review on Stay Hydrated On The Go With The Hydrapak UltraFlask Collapsible Water Bottle For Hydration Pack by Jamonte Hamilton

I use this bottle with my Salomon 1L running vest. As soft flasks go, it is okay. I prefer the types of flasks which have a larger opening, as it makes it easier to clean, but the wide mouth really doesn't serve the kind of purpose to which it is typically put.The most significant issue is that it is very difficult to close - to secure the lid you have to apply significant twisting force to it and the bottle,, but the only surface you have to grab onto on the flask is the collar right under where the flask threads on, which is of course flexible. If you grab lower, then the squeezing pressure forces the water out the top of the flask. You can tighten it, but it takes several seconds and some technique, whereas on any other bottle it is maybe a second and practically zero effort. The collars on the official Salomon flasks (ASIN: B07V7J8R8F) are approximately elliptical in shape and a little stiffer, so you can get a solid grip, and the caps go on as easy as any other bottle.The second issue is how it fits into the vest. In a Salomon vest, the circular lid doesn't really fit well - it protrudes awkwardly (in terms of how it feels and how it looks) from the top of the sleeve, and it only gets more awkward as the water in the flask decreases. It fits, but not as well as the official Salomon flasks, which have that oblong collar and narrow cap, which has no such issue.So this is okay for a generic soft flask, if you want to keep it in your pocket or bag and collapse it when it is empty. Much more convenient than hard plastic bottles for that purpose. However, for a running vest, try the Salomons or flasks of a similar design instead.