Rocker molding is an extra piece on the bottom rocker, so its the extension. It comes in gloss black standard or if you select CFV, in a different more agressive design in carbon fiber.
I ordered both carbon packages since the second one compliments the look of the functional one and you get carbon fiber from all angles of the car front to back. One of those I didnt want to wake up and regret not having.
Ungwei, order the BTH wheel even if you do only want the sport/standard seat. Make sure that RPO is selected. I am not sure where the assumption of wheel will be included in first 250 came from, would hate for you to miss out on that amazing wheel because of $500, I will try to get this clarified for sure.
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All views and opinions on here are my own and not those of Cadillac or GM.