Polyurethane. I did mine with the bumper on. You did it by yourself daigledangle? I had a helping hand as I wanted to shape it well and sit as flush as possible while my friend screwed it into place. The holes on the top of the lip where its near the fog lights bugged me so I bent it as far as I could then screwed it into place. Seems to be a tough lip. I scraped it a few times and the bottom appears to be virtually unscathed.