M12 Monopole® Photo showing the external locking bolt ( which has provision for a banana connector ) and the threaded cylinder into which the locking bolt known as the Spanana^TM bolt threads into.
The M12 Monopole® is machined from solid Copper billet and is a nominal 15.4mm in diameter.
It is electroplated with a minimum of 5.0+ microns of Pure Silver  and 1.0+ microns of Pure Gold.