i have fiberglass kits, so far as good is what i can say. i've scraped the front a couple of times, but because it was well made thick fiberglass, it has not cracked yet. one thing i like about fiberglass is it's easier to work with and modify than urethane. if you bought some ****tie fitting urethane kits, then you are fawked up. so if you decide to buy urethane rather than fiberglass kits, go for name brands like WW, xenon, or at least real BW