The Double Barrel running hydration pack is your trail and road running companion. It fits a wide range of sizes and thanks to no chest strap, it fits almost all ladies wonderfully. Small to big size guys too. The shoulder pockets use a stretchy material with an ultra soft neoprene closure to store up to 10 gels per side, your cell phone for running and keeping close at hand, and other key on the fly requirements. The rear cargo storage is a dual layered pocket. One shallow to reach your cell phone while running, and a main pocket that can hold nutrition needs for any trail, road, ultra running, or marathon event. There is also a shock cord area in between the bottle holders to hold your jacket or extra layer. Rethink the hydration pack with this one, it simplifies clean up, makes refills a breeze, and you can run with two different hydration options.