Alternator 172 cup

[Jackg123]

Hi I very recently brought a 172 cup and after a long drive a squealing sound started. Anyway i think it’s my alternator tensioner, a bolt seems to be missing. Im assuming the said bolt passes through alternator and into the bottom of tensioner. Anybody know what’s size bolt this is ?

 

[bloke]

M8 x 20mm ish.

 

[Jackg123]

M8 x 20mm ish.

Thanks for that