I picked up a large and 3 mediums to play with. Used them on a week long trip and they seem to be working out well. Right now I have my camping gear in the large box, food and kitchen kit in 2 of the medium boxes, and tools and spares in the 3rd medium. My rig has room for another medium box if I wanted to add it as well. My only issue so far has been the reinforcing ribs of the lids eat up a fair bit of room, so I may have to explore options to get rid of those. Also the keeper for one of the wheels on the large box came off and went AWOL, so the wheel can slide off the axle if you're rolling it around. I was actually going to ditch the wheels all together since they just waste space, but the wife liked them for when the tent isn't near the truck.
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I also looked at the DeWalt boxes and thought they were better built, but also at a higher price. Since I did this as an experiment I decided to go with the cheaper Ridgid boxes and I'm pretty happy with them.