Mirrors bolt

Could only be a 8 or 10mm, just measure it with a rule and then order your bolt, eg M8 x 20 is M8 thread with a 20mm long thread

 

Be a bit careful here as my 2011 Speed Triple mirrors are/were M10 fine thread.
If you forced a standard thread M10 bolt in it'll ruin the mirror holders if you ever decide to re-fit the original mirrors.
Oh and hello to everyone btw - my first post (meant to do a proper intro for my first post but saw this thread and wanted to reply).

 

Hi Trev,
M8 standard pitch is 1.25mm
M8 fine pitch is 1.00mm
Generally this type of fine pitch fixing is used to alleviate vibration slackening.
Mirrors are a good example of this, it also makes them easier to 'clamp' in the right position.