This is the gear that attaches directly to the motor.  The stock ones can be very hard to remove from the existing motor so I suggest just buying one of these whenever you replace a motor.

100% Brand New
Made of High Quality Material, Stronger And More Durable
Suitable for: Wltoys wl-toys144001 124019 124018 A959-B A959B A969B RC Car

Material: steel
color: As shown (There is slight color difference due to different batches)

Package Contents:
1 * Motor Gear
1 * Set Screw