We use a 2.0L Cleantech vertical hydration bladder with an auto shut-off bite valve, feed tube routing can be either over the shoulder or under the arm and cargo storage is 5.0L. The lightweight unique chest harness system is fully adjustable across the chest and around the waist that ensures a rock-solid fit, with Airline back ventilation that helps keep airflow between the bag and your back, sweat is kept to a minimum. There is a removeable tool roll included to store the essentials for getting you out of trouble, various storage pockets including one for a mobile phone that has a touch screen function and even a safety whistle!