This is the bottle that put Nalgene on the map.And after all these years it is still their best seller. It's design appears simple but there are over fifty years of manufacturing experience that go into creating a super durable, Leakproof bottle that is guaranteed for life. Graduations help you keep track of your fluid intake or serve as a useful guideline when mixing up a beverage in your Nalgene. Most backpacks have a pocket on the side to hold a bottle and those pockets were designed to accommodate a Nalgene bottle because hikers have trusted Nalgene for over twenty years.