Plumbing Questions? Ask a Plumbing Expert.
I don't follow your question. Those are meter connections not unions. There is a neoprene washer/gasket inside the nut. In most cases it can be re-used. If the connection leaks go to your municipal water department and ask them for a new gasket. I can't tell from the picture what size the meter is. If you can tell me the size of the pipe threads on the other end of the connection (where it connect to the water line) I can tell you what size the meter is