Rear brake cam shaft size?

Morning all just a quick question, are the rear brake cam shaft thickness size the same on Li series 1/2/3 innocenti and GP?
I have a series 1 cam and it won't fit in a GT casing, whole too small or cam shaft too big?
Cheers ove.
I have a series 1 cam and it won't fit in a GT casing, whole too small or cam shaft too big?
Cheers ove.