I have a Jansport womans Isis for longer trips. It has lots of pockets and a 70oz resevoir. Enough room for a jacket, wallet, keys etc. I like that the bladder is bigger on top so most of the weight is higher up on your back. For shorter trips I have a camelback pixie which only holds 35oz but has enough room for wallet, jacket etc. Plus you can zip the shoulder straps together to make it a one strap sling off the bike, oh and more importantly it was purple!