The Exped Bergen and Pocket liners are custom Exped products for the military. The package is the 3 fold dry bags that you need to waterproof a standard Bergen and side pockets. We also sell the Main bergen and the side pocket dry bags separately. The main dry bag is 140 Litres which is enough to take a full bergen load and still be rolled down and closed to make it waterproof. The side pockets are 13 Litres each, again to take a full load and still be closed properly.
Note: the image is not of the actual drybags, but of some other drybags so you get the idea.