Are you referring to this?
If so.. I haven't put mine on yet (get the car on Monday), but it appears to be painted plastic (softish, it bends somewhat easily, no clue beyond that). Going to contact Zetaproducts though, one edge of mine seems to be chipped or somesuch, it is sort of speckled, if that makes sense.
Edit: Should have read the product description, would have given me the answer. "
Made from durable ABS plastic that has been coated with a high-gloss chrome finish"