The arms themselves are really just 3 sets of dimensions.... body width, pivot length & adjuster offset.... the STAND they bolt to are what are head specific.

There may very well be some brand X head out there than uses same pivot length & rocker arm offset & body width as a W8 or W9 etc. I don't know what it would be, but would not surprise me if the same arm is used in some other application.

I've used different spec rockers on certain heads before than what T&D or Jesel originally supplied with that particular stand.... (usually different offset or body width)