I just learned that I had some on the front with my Alcoas. I took my wheels off for the first time and changed out some tires, and noticed them. I think the previous owner put them on quite some time ago, and they're made out of steel. Most wheel spacers I've seen these days are made out of aluminum. I believe they're 2", and I've gotten the impression that's a common size folks run to make the front match the rear a little better.