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 your BMW toolkit) in order to fit and remove it.
See tools.
For spare parts see filler pipe (part number 7659578) and o-ring (part number 1340901).
Also referred to as oil filler cap.
Chrome cap II was created for covering the gear oil filler...
Cover for the foot brake fluid reservoir, CNC machined of...
Made of high-quality aluminium and fits all four valve twins...