I would not want one on my back all day long, but it may be a handy way to stow extra water in areas where you may need extra and the pack design may be an easier form of carrying in the water I would use it more like an add-on to my pannier than a back pack though and just refill my bottles from it. Possible a good way to smuggle my bottle of Crown Royal around for my evening and morning coffee as well som folks look at you funny when you pull out a flask but it is common for a nip in you coffee up here especially in winter.