Agree with Matt. A more "original" looking knob from some other component would be nice. (lighter, radio, etc.) I found a post where Bill and I (and others) were discussing this. Bill posted the pics there also. I have had TF's with the cable operated electric wiper which operates a slider switch on the wiper motor. It is very much like the vacuum wiper system. I think the agreement is that this cable deal was used on early electric wipers. There was a transition. Maybe to use-up parts. I also think that the note "not for use with original electric motor" may mean that the early cable controlled switch can not be wired to a dash switch or their switch won't play with the latter wiper relay. I have emailed them.

See this and this.

Right is right, even if everyone is against it, and wrong is wrong, even if everyone is for it. - William Penn