Worked well for me.
I have only used it once, but thus far I am satisfied. Managed to fit sleeping bags and pads for three, two camping chairs, plus a couple of personal bags and some small odds and ends. Sturdy construction (once closed and locked). No major effect on gas mileage. Relatively quiet (notable noise, but can still have a normal conversation in side). Note: If you're a jump right in without the instructions kind of person, remember that you can only open one side at a time. I recommend this box!
For the price, the Rola cargo basket is a great option over its more expensive counterparts from Thule and Yakima. Easy to put together. With the extension added and to be installed on a large SUV such as our Armada, a second set of hands is definitely needed to get this onto the factory roof rack/rails. I would've given the Rola 5-stars but unfortunately, they don't offer locking brackets.