Rear wheel centre cover with emblem.
The holes in the covers aid cooling!
Measured temperature on the engine test stand (engine is cooled with a supercharger) without plug: 54,9C; with plug: 50,1C
Measured temperature after a tour of about 250km without plug: 53,4C; with plug: 49,4C.
Also referred to as wheel hub cover, rear axle cover.