The Active Skin 8 Set comes with two Soft Flasks in their dedicated chest pockest. These 500 ml bottles flatten as you drink, thus avoiding an air pocket which would make the liquid slosh around. In addition to running this kind of a pack works in other endurance sports as well. - 8 liter cargo space at the rear - Bottle pockets at the front - Two bottles included - Elastic cord at front - Compatible with 2 liter hydration reservoirs (not included) Choose the size according to chest circumference in centimeters: - 80-85 XXS - 85-91 XS - 91-97 S - 97-103 M - 103-109 L - 109-118 XL