I work outside for 10-12 hours a day and a regular sized Nalgene just doesn't hold enough water for me to last until lunch. This Water bottle parka not only holds the 48oz Nalgene but I'm able to strap it to my belt and not have to hold onto it or fiddle with it while doing my job. It also keeps your water cool in the heat and keeps from freezing in the cold. Monday through Friday I have this bad boy strapped to my hip like a baby and once this one wears out ill be getting a new one to replace it. Solid product Outdoor Research, as usual.