When installing the pilot bearing, one side has rubber around the outside base, one side does not... which side goes TOWARDS the pilot bearing?

The downpipe i'm installing has a EGT bung on it which I will not be using, what size bolt will plug this?

thanks

 

Rubber side to the pilot bearing. Don't forget to put a dab of lithium grease in there.

Usually the EGT bungs are 1/8 npt, but it all depends on who put it in.