Keeping hydrated doesn't mean you have to sacrifice half of your pack space to water bottles, just snag the Hydrapak Stow 500ml Water Bottle and you'll be on the way to hydration town without the bulk. This completely collapsible water bottle stows up to 500-milliliters of life-giving goodness for your hike, and features a loop that makes for easy carrying. When it's empty you can easily roll it up, and the carry loop doubles as a strap for keeping the bottle rolled up tight and out of the way, so you can toss it in your back pocket or whatever spare space you can muster in your pack. Because its made of flexible, ultra-durable TPU it can be folded to fit in the strange shaped small pockets, while still standing up to the rigors of camping, backpacking, and general trail abuse. Plus, it weighs in 80% lighter than most hard water bottles, so once its empty you'll barely notice you have it with you at all.