The Ortlieb Seat Pack is a waterproof seat bag that offers sizable storage space that can compress to a smaller size. The inside and bottom of the bag are stiffened, ensuring stability in bumpy terrain. Spacious, waterproof saddlebag with roll closure Ideal for bikepacking and touring Light weight sturdy PU laminated rip stop Nylon Air release valve to easily purge the bag of trapped air, allowing for tighter compression Heavy duty fabric used at the saddle rail mounting location Sturdy PE inner stiffener increases stability of the bag Elastic cords on the outside of the bag for quick fixing of light gear Saddlebag acts as mudguard Can be mounted to carbon seat posts Daisy chain with seven fixing locations runs along the underside of the bag, allowing a rear light to be fixed 3M Scotchlite reflectors