The USWE Rocket Softflask trades a standard narrow neck for a wide opening built for aid-station speed, so ice, electrolyte mix, and a fumbling hand at mile 40 all go in clean. The ultra-durable TPU flask collapses as it empties, cutting the bounce and sloshing that makes a half-full bottle annoying in a vest pocket. Made by HydraPak, the flask holds up to repeated fills without losing its shape. What Our Gearhead(R) Experts Are Saying:"I've pulled this out of the freezer the morning of a cold race and filled it with near-boiling water on a winter training run, and it handles both without stiffening up or leaking at the seams."