its fiberglass, the fitment is about 96% accurate . The body shop has to know what there doing to do this job correctly. Overall I'm quite happy with the look I was very nervous at first tho.
I have a magnetic as well and i found an imperfection in the paint on the back fender. I went to the ford dealership to see what they can do , they told me that the panel has to be painted over but they dont recommend it because they don't bake paint at the same high temperature the manufacturer...
I sold my factory 20" rims and kept the rubber to place on these new black rims which i found to work nice with the magnetic gray. I never thought i would buy black rims.