The ortlieb seat pack all systems go for your next bikepacking adventure conveniently mount the ortlieb seat pack to your seatpost with the help of two extra strong velcro straps in addition to its other duties the seatpost bag serves as a fender in off road terrain the spacious waterproof seat pack keeps your extra clothes dry go ahead and dial in the packrsquos volume from 8 to 165 liters via the roll closure on the side to meet your stowage needs use the convenient