This box is very long on a very short roof line. You will need a Thule rack system to mount it on if your factory racks are on the back portion of your car. The standard luggage rack that comes with the car won't work. It's not long enough to open the rear hatch while the Thule box is on the roof. You will need to raise it up 3" and move it forward 2". The Thule Rack with Aerobars will work. I use my Thule box all the time now I have full access to my vehicle.
2009 Lexus RX-350