I'm guessing it's the metal one, which is usually zinc plated or phosphate, not chrome. It goes on behind the carpet and keeps the seat belt bolt from bottoming out. There is usually one black plastic washer that goes on the bolt first, then the seat belt anchor, then through the carpet and thick washer. Convertibles probably weren't supposed to get them due to inner rocker panel clearance. It's a really tight fit for seat belts on a convertible.