WineCountryUA

First time EuRail user

If traveling primarily in Germany and Italy, but taking one non-stop train from Munch to Bologna -- ECB85.

Which countries need to be on the 3-country EuRail Select pass – Germany, Italy and???
Switzerland
Or Austria

ECB appears to transit Austria but was not planning on exiting

Or does it not matter?

There is a small thought of a side trip to Switzerland -- hence the question but unlikely. So unlikely would not wish to purchase 4 country pass.

Thanks in advance for your help