Osprey Skimmer 16 Hydration Pack - Women's - 2.5 Liters
This pack is just about the perfect size for a day hike. It's lightweight and has a hydration pack that will hold 2.5 liters hands-free! It's also cute. Because that's important too. If you're new to buying hiking packs (not Jansport), I also recommend getting one made "for women". It's not hype. There really is a difference in how the weight is distributed and how they hang on the body.