For all those odds and ends you want to have easy-access to while on your bikepacking adventures. From Ortlieb:
What should you do with all those small, but important extras on your bikepacking tour? The best place to put your snacks, smartphone, rain slicker and other items is in your ORTLIEB Accessory-Pack. This convenient volume expander for your Handlebar-Pack keeps your things secure, absolutely waterproof and quickly accessible at all times.
Use the metal hooks to securely attach the Accessory-Pack to the four points of attachment on the Handlebar-Pack. And if you don’t plan on spending the night outdoors and don’t need your Handlebar-Pack, you can still use your Accessory-Pack as a handlebar bag thanks to its pre-mounted Velcro straps. You can even use the carrying strap to transform the lightweight bag into a shoulder or hip bag.