I go this on Amazon to move my son to Oklahoma. We filled it with stuff, strapped it on, and drove out there. Then we unloaded his stuff and I brought it back to Chico.
It was easy to put on, and we didn't have any problems with it. But I don't plan to move again, so I am selling it. According to the specs, it holds 15-20 cu ft of stuff. I put light-weight things like clothes, towels, sleeping bag, etc, since it was on my car roof.)
The first picture shows the bag itself (it is about 4 ft long, and 3.5 ft wide, although it looks smaller in the picture.) The second picture shows a pad (to protect the paint on your roof against abrasion--mine was not scratched at all from the trip), a bag that held this pad and the straps (which are all attached now) and an instruction card.