Collapsible flask construction solves the problem of carrying empty bottles that take up space after you drink. The Quick Stow holds twenty-one ounces when full but folds down small enough to fit in a pocket once empty, which matters when you're running long enough to need water but don't want to carry bulk on the way back. The thermoplastic polyurethane body is flexible enough to collapse but durable enough to handle repeated folding without developing leaks or weak spots that force you to replace the flask after a few months of use. At forty grams, it weighs less than most rigid bottles even when accounting for the bite valve and cap assembly.

The one-piece silicone bite valve self-seals after each drink so you're not dealing with drips or having to close anything manually while you're moving. You bite down to open the valve, release to seal it—simple enough to use without breaking stride or taking your eyes off the trail ahead. CamelBak designed the flask to fit the front pockets of their running vests where you can reach it without removing your pack or breaking rhythm during a run. The slim profile slides into vest pockets, waist belts, or even a jersey pocket without creating bulk that bounces around or shifts your center of gravity when you're trying to maintain form on technical terrain.

Volume markers printed on the flask body show measurements in both ounces and milliliters, which helps when you're mixing electrolyte powder or tracking hydration intake during training runs. If you're dialing in your hydration strategy for race day, having visible markers means you know exactly how much you've consumed without guessing or doing mental math while exhausted. The cap is top-rack dishwasher safe, which simplifies cleaning after runs where you've mixed in drink mixes or gels that leave residue. A hanging loop lets you suspend the flask upside down for drainage and drying—water doesn't pool in corners where it can develop odors or residue between uses. The flask body construction uses eighty percent thermoplastic polyurethane with fifteen percent polypropylene copolymers and five percent silicone for the valve components.