Nathan VaporKrar Running Belt

I like this belt because I can position the water on my side (by rotating the belt), so it's extremely comfortable, but it's also a really simple belt, and simple is good. The version of this that has a zipper is the superior choice, as the velcro version allows the water to slip out from time to time. It holds one quart in a soft flask, which isn't a whole lot for a long run on a hot day, but I've used it many times and it's been great.