I use mine for carrying my locks around. My Kryptonite u-lock fits perfectly in the front zip pocket with the lock in the bottom and the u-shape of the bar following the contour of the u-shape camelback pocket -- fits like a glove. I also throw my front wheel small chain lock in their as well....
When I take longish rides (20m or more) I typically leave the locks out and use it for water. Works really well, albeit a bit of a sweat factory laying on your back as it does.