Got mine from a fellow rally participant at Nashville. Don't know how effective they are yet as the front of the trailer was already covered in bugs, dirt, diesel soot etc. But the price was right - $25
FYI, the set I got was being sold because the truck (GM) was a newer model with that "hot" exhaust issue, and it was directly affecting the mud flap, to the point of damaging it from the heat. Not an issue on our 2006 GMC.