Object on bottom of Prius behind front wheels?

[pasadena_commut]

There is an object on the bottom of the Prius behind each front wheel. It starts an inch or so behind the wheel well and runs along the bottom of the car for about 7". I could never get a good view of one from the side of a Prius, and was too embarrassed to crawl under a car to look (I don't own one). When viewed from the side this thing looks vaguely like a plastic cheese grater.

What is it called and what does it do?

[SVOboy]

If I'm thinking of what you're thinking of I think it's an aero diffuser for the wheels.

[MetroMPG]

Mystery to me. I can't recall ever noticing what you're describing. Maybe one of our Prius drivers will chime in (with pics!)

[donee]

Hi Pasadena...,

Its a belly pan add-on. Its smooths out the surface, except for the holes in it. From what I remember, it more like 3 foot long, and goes almost back to the rear wheels.