GPS Mirror Mount - What mm?

[countfunkula]

I have an '06 Monster 620 and I'm looking to buy a GPS mount to go into stock mirror mounts (I have bar end mirrors now). Does anyone know what mm size mount I need. I've read that the older Monsters have 11mm and that newer have 8mm, but can't find a definitive source.

Thanks!
The Count

[stopintime]

10 mm