Originally Posted by jvaliensi

All the decent aluminum arms I have found are threaded for 3mm or 4-40. And they tend to be thicker than the metal clevis can go over.
I had found non-threaded aluminum arms but they were pretty thin and weak and I wouldn't use them.
Promodeler sells good quality plastic arms w/ 25 tooth spline.
3D models are using long threaded aluminum arms with ball links on both ends. The geometry between the servo mount and surface horns is optimized for this setup. I find the jets are setup for the clevis on one end or both.
I'd like to use metal arms if I could find what I needed. I've had plastic arms fracture. They become brittle when it is cold.