I run with one I bought between 5 to 10 years ago. It is an Ultimate water bottle with a kickback valve. In 30+C weather, it takes an additional 30min for a solid bottle of ice to fully melt. Without the insulation, it takes only 30min for all the ice to fully melt. One thing I have noticed is that my fingers get wrinkled as if I have been doing dishes or swimming for a long time. As for balance, I used to switch hands every 30min, but now just run with it in my left hand. Most people who are right handed are weaker on their left side, so I figure that will just help to balance that out anyway. Also, for proper balance, the road would have to be completely flat.