The CamelBak Vantage 40 Hydration Pack has a three-liter water reservoir, enough cargo space for all-day or quick overnight trips, and a waterproof roll-top. The roll top means when it starts drizzling on your hike, your extra layers and snacks wont get all soggy. An aluminum center stay and a vented, load-bearing waist-belt stabilize your load, and CamelBaks D.V.I.S. Back Panel has independent pods that distribute weight comfortably and provide ridiculously airy, multi-directional ventilation. The medium Vantage Hydration Pack works well for 18-20-inch torso lengths, while the large Vantage fits 20-22-inch torsos.