Listed as a "Standard Feature" for the Scion xB's is:

Exterior Ground Effects Kit (includes front air dam, rocker panel extensions, and rear valance panel)

What is this? I really don't know anything about this kind of stuff. Thanks for you help.

 

xB's come stock with a lip kit on the lower body of the car. If you look closely, you'll notice that the front and rear bumper are two pieces. The lower piece is the lip kit/ground effects kit.

Rocker panel extensions are the side skirts on the car (right under your door)