Hydrate effortlessly with this 500mL flask, designed for compatibility with vestpacks. A WingStay™ removable stabilizer prevents bounce, while a wide-mouth opening makes it easy to load ice or mix in electrolytes. A high-flow valve, easy-grip twist cap and tapered shape simplify hydration. Crafted with durable TPU and RF-welded seams, and compatible with the UltraFlask Filter Cap (sold separately).