The Thule Rapid Aero Foot Pack 400XTR includes four towers that work exclusively with the Thule Rapid Aero Bars. This system integrates the tower and the load bars to create a seamless look. The Rapid Aero Foot Pack needs car-specific fit-kits and load bars which can be determined by clicking the Fit Guide tab below. The clips and pads are sold in Thule's Fit Kit they clip around the edges of your roof.
Click here to launch fit guide.
It works - what more can you ask for. Also, this site had the best price I could find!