This gearset is for AX-18A servos only. It is not compatible with AX-12+ or AX-18F, as the gear shape is different.
The AX-18A Gear set is designed to replace/repair AX-18A servos that may
exhibit worn or broken gears.
Replacing them with this kit will restore the servo to it's original working condition.
Broken gears can be easily detcted by turning off the servo and manually rotation the servo all the way. If loose or harder spots are felt during the movement or if you hear clicking noises, then gears may have worn out or broken.
Video: Replacing the Gearset