The 2-In-1 Travel 40L Backpack zips together as a single 40-liter travel backpack for transit days, then splits into a 34-liter base pack and a 16-liter daypack once the trip settles in. The base pack stays at the hotel while the daypack heads out for the day, and the two halves rejoin for the next flight. What Our Gearhead(R) Experts Are Saying:"For a one-bag trip, the base pack takes a large packing cube laid flat, and a second cube stacks on top as long as neither is stuffed full. That keeps clothes in grab-and-go blocks instead of loose in the pack. Packed to the brim, the pack gets thick and heavy, so I stop short of full."