What does this icon in the garage indicate?

What does this icon in the garage indicate? - Metal post with direction indicator on avenue with high skyscrapers in New York

In Rocket League, what does this icon in the garage mean?

I have tried:

Steam question which just says "some items are just available for some cars", which is not really helpful.
I disagree with this Reddit answer, because I think that should be an exclamation mark on the right side and it should disappear once the item was selected.

rocket-league

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What does this icon in the garage indicate? - Crop person using recycling app on smartphone against coffee

What does this icon in the garage indicate? - Dirty Roll Up Door

What does this icon in the garage indicate? - Selective color of gray luxury sports car parked on floor in center of car park

Need for Speed Heat - Ultimate parts explained

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