The sheer variety of hydration options these days is overwhelming, but you can rest assured that however you hydrate, Camelbak has a solution for you. Their Ultra LR (pictured) and Marathoner hydration vests solve the same problem in two different ways.
Both vests have an overall low profile and very useful (why don't more packs have these?) wide shoulder straps with a good-sized mesh pocket on each. The pockets are big enough for food or extra water, cameras, cell phones, even a compact wind jacket. The fit is snug and contoured, with not one but two sternum straps to really dial it in. Runners, bikers, scramblers and anyone who moves around a lot will appreciate the fit.
Both Camelbaks have 70oz. hydration bladders, but where the Marathoner uses a standard vertical carry format, the Ultra LR carries lumbar style, horizontally. Because of this the Ultra LR also has a hip belt, unlike the Marathoner. The other big difference is the cargo capacity. The Ultra LR has a larger main pocket and adds two medium pockets on the padded hip belt.
Both vests use Camelbaks excellent delivery systems, with Antidote reservoirs, Big Bite valves and Quick Link fast connectors between the tube and bladder. Both the Ultra LR lumbar vest and the standard format Marathoner are excellent solutions. If you're a traditionalist wanting to go uberlight, the Marathoner is for you. If you want to pack more gear and distribute the weight around a lower center of gravity, check out the Ultra LR. If there's some other combination of capacity and carry style you desire, check out Camelbak's web site and prepare to get dizzy with options.
Marathoner $74.99 (on sale from $100.00) at REI