This is the middle clothing compartment. The compression straps attach to the wall that doesn't have the closed cell foam inside it. It is wider than the first clothing compartment, but not quite as wide as the third clothing compartment. Note that the closed cell foam is only on the dividing walls between the first and second compartment and the third compartment and the backpack straps.

I'm okay with that as it saves weight by not having it between the two compartments. The lack of foam around the side may pose an issue for people who are trying to put computers or other electronics inside, but it has the benefit that it allows the exterior compression straps to more easily compress the bag and shrink it down if it is not completely full. I really liked this feature as it let the bag shrink down to a size comparable to a tri-fold garment bag when I had just one clothing bundle in the third clothing compartment on the first trip I took with the bag. The fabric dividing wall between this and the third compartment is a plus in my mind as it makes it easy to use one compartment for clean clothes and one for dirty if you're on a multi-day, multi stop trip.