Thanks to our patented Expandable Volume Technology, the tankbag's volume is continuously adjustable between 13 and 20 liter. To expand the enduro tank bag, simply release the four velcro straps and pull the outer part upwards. To reduce the volume, simply pull the straps until the required volume is reached. In our opinion, a simple and very comfortable solution. The side walls are stiffened and a waterproof membrane between the sliding parts avoids the intrusion of water and dust.