One vital thing that you need when taking a hike or going on a walk / run, almost more important than wearing the right shoes, is good ole H20! What I love about this Hydration Pack is the size. It's not to big that you feel like your carrying enough to get you up Everest and small enough to be comfortable. Holds up to a liter of water. Fun Fact: You could also fill it with your favorite "beverage" ;) and bring to festivals, etc.