We tested by running through airports and racing after buses, trains, and boats around the world. We brought them on a climbing trip to the French Alps, spent a month dragging them in sleds across the glaciers of the Alaska Range and ditched them in the forest for three rainy weeks in Patagonia. Our trips through South America even resulted in two getting stolen, which we had to replace. After having carried nearly all of these on various expeditions to three different continents, we also did side-by-side testing by overloading each one with 55 pounds ("Because that's the weight I sometimes try and get away with when I check my bags") and walking through Sea-Tac airport to fairly compare each model. We beat them up intentionally to see if any showed more early signs of wear than others. We placed towels in each and then sprayed them down with a hose in our driveway to test weather resistance.