The ortlieb airflex 11 backpack the first trip will prove it this backpack makes your life lighter compact design and 11 liter packing volume make the airflex 11 a full featured yet sleek and waterproof pack with convenient roll closure the flex wire system with comfortable padding offers real carrying comfort the adjustable compression cord serves for fixing a bike helmet or light jacket two outer pockets not waterproof offer space for small items which should be quickly accessible