I was servicing a very nice tiagra 12 for a fellow, and noticed it had a sst tube spacer between the bearings on the spool shaft. It might be a factory part and original equipment, I dunno?
Anyway it measured .936'' in length and the spool shaft measures .277'' in diameter. So it must be about .280-.285''inside diameter.
This info might help someone someday?????????? gst.
I have not seen any Tiagra's with a spool bearing spacer.