There is a drilling in the side of the plug in which you can put a size 3 Allen key or a Torx key T10 (usually found in the your BMW toolkit) in order to fit and remove it.
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Also referred to as oil filler cap.
Cover for the brake fluid reservoir. Honed from top grade...
These covers for the open holes of the engine mounting are...
These covers for the open holes of the rear engine mounting...