I LOVE THIS PACK! It has room for all my needs, plus everyone else's! I went on a week-long ski trip in Park City and fit everyones sandwiches, camera's, bevvies, and extra gear no problem. The great thing about this bag is that it expands if I have a lot to stuff inside, but can tighten up into a more compact size if I only have a few items to store. I also use this bag as my carry-on on the plane, which is the perfect size and I do not need a second item, such as a purse. The bag is hydration pack compatible, but if you choose not to use one it's no problem. I did have to safety pin my hydration pack to the bag lining to keep it upright, but other, it rocks!