What is this? (no prize :)

[hashluck]

I was replacing the mirror glass on one of my S2s (primarily to give me a blind spot view which does work very well with the new glass fitted) and I was intrigued by this black plastic block with an arrow on it. This is on the passenger side only, there is not one on the driver side and the casting is different. Assembled experts - what the hell is it and what is it for?

4723223B-663F-41F2-83FA-FDC86DC20050.JPG 4723223B-663F-41F2-83FA-FDC86DC20050.JPG

[Nuvo]

Interesting, I don't rememberever seeing one of those before. Is it a rubber block to stop vibrations or reduce motor noise maybe?