Not only does it hold a water bottle, it holds lots of other stuff too. It's got panels of PALS webbing, a loop field for patches and a good sized pocket on the front. I use mine to carry a bottle, water sanitization stuff, a good knife, fire gear, a HeatSheets blanket and my Ritter PSP. It's much more than a bottle carrier, it's a system.
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“I'd rather have questions that cannot be answered than answers that can't be questioned.” —Richard Feynman