Nathan 18oz Insulated Soft Flask – Collapsible Running Water Bottle with Bite Valve, Fits Nathan Hydration Vests

The insulation actually works. My water stayed cold through a whole 10-miler in August heat, and the bite valve doesn't leak in my vest pocket.

Slides right into the front pockets of my VaporHowe and stays put. Collapses down as I drink so it doesn't bounce. Buying a second one.

Took me a couple runs to get used to the bite valve flow, but now I love it. Keeps water noticeably cooler than my old soft flask.

I've used cheap soft flasks that tasted like plastic forever. This one rinsed clean after one soak and the insulation is legit. Half marathon training approved.

Heavier than a non-insulated flask when full, but the cold water on hot days is worth the trade-off. Shrinks down nicely as you drink.

Works well and fits my vest, but the insulated material makes it harder to collapse fully compared to my old flask. Fine overall.

Mine seeps from the cap threads when the vest pocket compresses it. Kept my phone damp. Might be a defect, but I returned it.

Cold water, no leaks, fits perfectly. Done.

I run desert trails and ice used to melt in 30 minutes. This flask kept my water cold for nearly two hours last weekend, which honestly surprised me. The 18oz size is enough for shorter loops and it collapses flat for packing out. The wide mouth accepts ice cubes from my freezer trays, which was a big selling point. No funky taste, no leaks, no regrets.

Bought two for my Nathan vest before a Rim-to-Rim hike. Both performed flawlessly — no leaking, easy to drink while moving, and the insulation kept things palatable in the heat. Docking a star because they're a little bulky when nearly empty.

At 62 I finally stopped carrying rigid bottles that bruise my hands on long runs. This soft flask is easy to squeeze, easy to grip, and the bite valve is gentle on my jaw. Fits my old Nathan vest pockets too, even though it's the insulated version.