Necessary for the regulation from above with the Topkey

The twist lock-ring fixes the movement of the head necessary for the regulation from above with the Topkey, allowing the switch to the lateral- adjustment mode which is useful in the cases where an additional support is positioned at the centre of a large tile. It is therefore sufficient to insert the twist lock-ring in the special slot in the centre of the Balance Pro head to permit the adjustment of the support without having to remove the tile. The two rings can be used simultaneously.