Don't let anyone tell you how to get hydrated; CamelBak's genius Octane 18X Hydration Backpack lets you customize the shape and capacity of your pack to suit your own demands, whatever they be. From 671 to 915 cubic inches of storage, you can determine what's essential and what's unnecessary. From an ultra-sleek trail water pack to a small backpack, the Octane isn't quite sure about commitment, and that's probably fine with you. You'll find yourself able to go about three hours with this three-liter Antidote reservoir before having to refuel. Either way you wear it, the weight of this pack alone won't add more than a pound to your activity because of its ultra-light construction. An extra coating of DWR and PU ensure that rain and wind won't have anything to do with your gear. A small assortment of cargo, harness, front, and stash pockets won't short you of any storage options you can imagine for your phone, wallet, music, and snacks. Reflective on both front and back, the Octane 18X also features a safety whistle for added security during evening and night treks. Season after season, CamelBak's super scientists have been hard at work refining and perfecting the Antidote reservoir, the industry's most popular solution to hydration. At the turn of a cap (a quarter turn to be exact) , you can open or close the reservoir, refilling and securing it again in seconds. Center baffling and a sleek design prevent your water from jostling about inside your pack while running, hiking, or hitting the park. When not off exploring the world, simply disconnect the tube using the Quick Link System and hang up the Antidote for proper drying or storage. Since last year, CamelBak's go-to reservoir system has actually lost some weight, reducing bulk in the fill port and offering you that much more convenience.