Hi Jim,

they are carbon-reinforced plastic. (I think like the heavy-duty Hitec arms) I think I'm going to order some to get a feel for them.
Otherwise I'll have to go for nylon arms and traditional clevises. Clevis + alu doesn't work for me.

If anyone knows of a alu version of these please let us know

@Carsten, I don't think the twisting of the arms is the problem when using the alu ones, but the load they pose on the output gear/bearing combination - although the ball at least is on the right side of the the arm.

Nice (quick!) build - I havent even had a chance to start!!