Jake was looking at a backpack kinda like this in EMS, so I made him one for his birthday. I borrowed it at one point and decided I liked it, so I made me one too. They are expandable via side zippers, plus two different compression straps on each side. also have laptop slots against the back accessible by a zipper on the side that doesn’t really show in the photos. I’ve found mine to be very comfortable to carry, even with a large load.