When youve only got half a day to get your adventure in, the midsized North Face Gulper Hydration Backpack provides just the right space for essentials. If you get thirsty take a long swig from the articulated magnetic bite valve of the 70-oz Nalgene reservoir. If you get lost blow on the Safe-T whistle on the Sternum strap. When you cant see rely on the reflective hits to find your pack storage. When its become ridiculous to keep moving dive into to the large main compartment, internal organizer, and side stretch woven pockets to put on every stitch of clothing, then ration your snacks for the long night out. Oops, better planning next time. When the guide book says a day, believe it.