Supplied in the kit is a carbon fiber arm that screws onto a round Futaba servo wheel, just like the rudder arm. The linkage hole is about 22.5 mm from the center. I choose to use the Dubro heavy duty arms which also has a hole 22.5 mm from the center. I have had no issues with these in the past and it saves a little over 2g per arm compared to the supplied set up. And yes I know taking pictures of a black object on a gray towel was the not the best idea :)