Specifications 3 l 350 g 130 g bladder 28 x 18 x 8 cm airo flex airo flex is an extremely sturdy material that is both permeable and flexible we use it for our top quality hip belts to ensure optimum load transfer to the hips with simultaneous maximum ventilation ndash for utmost carrying comfort venti flap the venti flap system enables folding the back piece away for maximum ventilation and thus enhanced carrying comfort during longer ascents you can increase the distance to your ba