When ultra runner Scott Jurek set out on his record setting 43 day Appalachian Trail run, he relied on the Ultimate Direction SJ Ultra 3. 0 Hydration vest to carry all the water and calories he needed along the way. Inherently stable, the vest design eliminates bounce, and it holds water bottles in the front of the pack for easy access and accommodates a reservoir in the back for endurance runs. Bombproof, featherweight, and flexible mono mesh fabric along the inside of the vest keeps everything together in a lean, low profile package for a minimalist fit and feel. A total volume of about 518 cubic inches means you can take along a light layer, gels, or extra hydration on your epic outings.