These 13T gears are made especially due to the huge demand and they have been tested by different users who were very positiv about them but please note that mounting the gear is a bit harder than usual.
Mounting has to be done carefully by first removing the backingplate in which the brushes are placed before pressing on the new gear. If you not do this, you risk damaging the axle.
In the ad are photos of the new gear pressed onto the motor. Good luck!!