what size o-ring is used to mount smiths instruments on 750 GTs?

[stevefzr]

Does anyone know what size o-ring I need for the smiths instrument mounts on a 73 GT?

 

[Paul Marx]

Does anyone know what size o-ring I need for the smiths instrument mounts on a 73 GT? View attachment 103238

I've got this measurement in my notes.
Torique porte instrument Smiths 104,14 x 5,33

Paul