The Navik connecting rod from Mister Vee comes with the length set at more or less the correct length.
However, this length may need or in fact require to be fine tuned.
If the length is not set correctly you will notice the pendulum rudder not tracking vertically when the boat is moving forward and the windvane is locked.
If you sail with a pendulum rudder that is not tracking correctly, your Navik may be damaged beyond repair!
Adjusting the length
If you hold the end of the connector (where the stainless steel pin goes through the black plastic) gently with pliers, you can release the brass nut which is tightened against the ball connector.
Then you can adjust how much of the brass screw goes in to the ball connector to lengthen or shorten the connecting rod.
Be sure to tighten the nut against the ball connector again to lock the length.
The adjustment you need may be a very small amount like a millimeter, and you may need to make the adjustment more then once to get it right.
The length is set correctly when the pendulum rudder is in line with the boats mast when the boat is moving forward (without the boats engine engaged!) and the windvane is locked in neutral.