THERE ARE 3 ROTOR ARMS
EARLY WITH A VERY LARGE HOLE FOR INSERTION ONTO THE SHAFT
A MEDIUM SIZED HOLE
A SMALL HOLE - APPROX 10MM

I'll need to know which - the most common is the medium sized unit - they can vary - there seems to be no rhyme or reason .. yet

brands can vary so email me if you are choosy
typically beru qh valeo lucas