They are extremely tough. I appreciate that he makes a pretty small one. I don't know how space efficient the design is, i reckon it depends on what you're packing. I like mine, though I've been ridiculed by other cavers for having too small of a pack. On a long survey trip my wife asked for some painkiller, which I had neglected to bring. We got some from another caver and for the rest of the trip had to endure constant jokes about the lack of space in my pack for an aspirin tablet.