This control horn fits ø6 (6mm diameter) standard-size 25T spline servos such as ProModeler, Futaba, MKS, and SAVOX. Unfamiliar with our steering servos? Check out these two;
Note; the servo arm is specifically designed for use in the very popular TRAXXAS X-MAXX for steering. Thus, the arm's bearing support is sized to be a slip fit within a 10mm ID bearing (as fitting to that truck).
Finally, we get a lot of queries regarding whacking off one of the mounting tab ears on a servo (to make it fit an X-MAXX with their accessory adapter), specifically whether this affects the warranty. While we can't speak for other manufacturer's policies, it does not affect your ProModeler warranty, which is 1-year parts and labor against defects in materials and workmanship. The point being, what you do to your servo's case, which doesn't affect the guts and operation, is just none of our business!