USWE Pace 2L Running Vest Hydration Pack with 2 x 500ml UltraFlask, Backpack for Men and Women, White Black, L-XLThe two included 500ml Ultraflasks are placed in a 45 degrees angle front pockets for an outstanding comfort. The hydration vest features are intended for on the go access, including a front pole attachment, 2x quick stash front pockets, 2x energy food shoulder pockets, and 2x zippered stash back pockets. SIZE GUIDE: Measure your chest size just below your armpits: S M: 31. 5 36 inches (80 92 cm). M L: 34 38. 5 inches (86 98 cm). L XL: 36 41 inches