that run under the rocker panels? Because I have no idea what they do, except slowly destroy the car.
Sister's Mazda6 failed inspection because of heavy corrosion damage along the panels under those strips. There was a ton of salt and dried mud sandwhiched between the metal and the plastic; all it needs is a bit of moisture and the sills would resume rusting, all the while car is sitting in a garage!
I tore out the plastics, plugged the holes, fixed the rust and applied some underbody coating. At the reinspection the officer had to ask where the damage had been
He couldn't figure out either why the factory added such totally useless and harmful plastic junk bits.