Yet another comparison (air-gap carb spacers)
It's just a mr gasket or whatever from the little hot rod section at pep boys. You know the display with the chrome dice valve caps and starter blankets. I took the 4 hole and cut open the back two holes into one hole. It comes with the open and 4 hole- the plastic insert is slightly tapered to drop into the aluminum square casting.
I really liked the 2 hole on the primaries for street driving.
Good luck!
Radar