Bought this to ship my backpack to Spain to walk the Camino. I used it to back an Osprey 55L pack and there was MORE than enough room. Used another to ship a Gregory 55L pack and that too left lots of room. I bet you could fit a 70L pack without any problems. The bag folded or stuffed into a pocket for storage. They were not that heavy and we packed them on the trip to use to fly packs back. I would use again and they held up well. It had a strap to allow to carry with items in bag.