OK, I'm taking a chance...

Does anyone know what size nut holds the cable motor to the actual cable for the sunroof? it's NOT the plastic, round nut that you can screw by hand. It's the metal nut that holds the motor together. By screwing/unscrewing you can tighten/loosen the tension on the sunroof cable.

Mine is missing... and I've tried several different sizes.

I know this is a toughy... but thanks!!
Michael B.