Hydrapak UltraFlask Speed 600ml Go big. The largest of Hydrapak's ultra-light series, the UltraFlask Speed 600 holds more so you can go the distance. Its soft material allows it to fit snugly in most vest pockets and it shrinks as you drink to minimise water movement. Topped with their newest SpeedFill cap feature that makes aid station refills a breeze. Constructed using a soft material that conforms to most hydration vests, belts or pack pockets, the bottle frees up your hands. A tube can be used to drink from at any time with little fuss and hassle. As you drink, the bottle shrinks, meaning that there is less water movement. As well as this it can be twisted or collapsed to a quarter of its size. This makes it easily storable in a fully packed bag, or even small enough to put in your pocket. Featuring a SpeedFill cap, the bottle flips open for quick refills and snaps closed for a spill-proof seal. As well as this, the high-flow bite valve auto-seals after each sip, e