They are anodized aluminum. The anodizing needs to be removed, then they can be straightened and polished. They can then be re-anodized, which is of coarse expensive, or you can just go with the polished aluminum, which looks just fine. They are susceptible to oxidation, but if kept in a dry garage, should be no problem. Mine were done 4 or 5 Years ago, and have been on the car for 3 years. I just use detail polish on them and they look great. If they do ever show any sign of oxidation I will use Mother's aluminum polish on them, hand polishing.