I'll ask my DP. It was small, had three pump suction cups and holds up to 11 lbs.
Basically, it has 3 large suction cups. Maybe a little smaller then a baseball each. You push them onto the car, and pump each one till they firmly stick.
This is a much more advanced model. But, it basically looked like this. If I find a real picture, you'll see it's much cheaper then this one.
It scared the hell out of me. He didn't want to put his T5 (I think that's what he has) on it. Because this was the first time he was trying it out.
We did go over quite a few pot holes and bumps and it didn't move. So, as long as you apply it correctly it works great.