How big is a (normal) German Shepherds neck?

I would recommend getting a mix between large and extra large. Some of the shepherds at the rescue group might have come from abusive homes and would be smaller than healthy shepherd. Older shepherds tend to be heavier so they would need larger collars. Also, there are different types of shepherds within the breed. White German Shepherds and Old Fashioned American German Shepherds tend to have fuller necks than American Show or West German. I think the rescue group would appreciate a variety.