You could also try a product called a neverreach. It clips onto your seatpost with a straw that runs across to your bars, and holds a lot of water. I tried this when the weight of a camel back was bugging me. BUT, I decided I didn't like the cleaning involved with either the never reach or camelback, so now I use good old fashioned bottles. I freeze one the night before, and in the south texas heat it melts in no time.