[DanMan32]

As far as effectiveness, I watched a large rock (1 1/2 inch) ricochet off one lamp assy on the highway with no damage. I suspect it would have cracked the lamp lens without the protection. I was just happy it missed the windshield, but on reflection, the windshield is less expensive than the lamp assy.!!

How in the world did you do that? The fog lamps aren't visible from the cabin. Were you in a pace car driving in front of the Prius, or did you mount a camera to the front grille?