I originally started with a 70 oz Vaude hydration pack, but it chafed my neck. I tried a 50 oz Camelbak Siren, but it made my back & neck ache on long rides. Then I converted a Camelbak FlashFlo 45 oz to a handlebar mount. That fixed the aches, but left no room for my raingear. I moved the bladder into a larger lumbar pack so that my handlebar bag carrys my food, maps, camera, and raingear and the lumbar pack handles water, keys, wallet, etc. On long rides I carry an extra bottle in a cage to refill the bladder. This works well for me.