An extension bar for a ball-and-socket joint.  Created to move the phone closer to the user from the windscreen mount, but it can be used anywhere there's a ball-and-socket joint.  It can be resized 120mm to over 180mm and locked into place.

Print in ABS or PETG or similar, so it survives inside a car in the summer.

You need a 25mm M3 bolt to strengthen the neck; the first print failed very quickly there.

The OpenScad source requires the STLs from the Open Source Ball Joint, but since that's an 18mm ball and I needed 20mm, it's resized to suit.  The extension bar is sized to match the end-faces of the resized STLs.  If you want a longer or shorter bar, alter the connBot/connTop in the source.