Clutch Master cylinder thread size for union on 3500s

[DamianZ28]

Hi Guys, Embarressingly I cannot remember for the life of me the actual thread size for the union fitting for my clutch master cylinder , its a 3500s version.

I ask as I want to get a flexi staniless version made up, I got a copper version but not very flexible, the SD1 slave cylinder is an M12 fine thread.

Thanks a lot Damian