I got one of these to put on top of my Ford E-350 after building it out and moving into it full time. I can say that it was a life (and space) saver with the capacity it held and the room it allowed me to have inside the van. Camp chairs, sleeping bags, backpacks, loads of climbing gear, slack line, hiking gear, and any other miscellaneous things worthy of traveling with.
A couple weeks ago my van was stolen and the build I spent months on was destroyed inside. They stole all of the valuable electronics: battery, inverter, solar panel off the roof, stole my Dometic fridge, just utterly ripped it up and defiled it. They tried getting into the Yakima Rocketbox by drilling through the lock. This only disengaged the release button so there was no way of getting in. They tried breaking the plastic around it but were not successful. When the van was recovered, I was able to get into the box from the other side with my key to see my belongings still in there.
I am very satisfied with the quality of this thing, though unfortunately mine is ruined now. It served its purpose so well and kept my things safe in the worst case scenario. I will definitely be looking at Yakima in the future to get a replacement.