I remember seeing these a little while ago. It's definitely a cool idea. You'd think they could just put on some non functional sidewalls so it would look like any other tire.

Edit: Yeah nevermind, I don't think I saw the "tweel." I think I just saw a set of tires using the same concept mounted on some normal wheels.

Edit part deux: NM, they were in fact the tweels. I guess they just put a silver finish on the wheel portion: