Simple gears designed for servo and rudder. The larger servo gear fits onto a 4 arm servo horn, the smaller gear has a 1/8 center bore and a hole for a brass heat set insert. McMaster part94459A270. If printed well + heat set installed correctly, very hard to strip out unlike resin rudder gears. I use this setup in most of my boats.
Servo/Rudder Gears 1.0
Servo/Rudder Gears