No luck finding this out for you. I found on a Mercedes owner site posting where the member said he found these on the floor by his brake pedal after having the dealer replace a water pump. A parts website referenced the part being associated with the Front Left Wheelhouse. Without taking the wheel off I used a mirror and flashlight to look around and behind the front wheel on my convertible and didn't see it, but my view was limited. I also did a search for "plug" in the 2004 Crossfire parts manual and found a plugs chart on page 227. The Chrysler part number is: 05099362AA. There is no parts diagram reference where this goes. This certainly appears to be a body sheet metal or frame plug.