If you're completely new to RC cars and order the wrong parts like me... Than you may need this :)

This is a connector piece for when you've got a motor where the mounting screws are on the same side as the shaft.
Originally, you're supposed to use one of those hexagonal couplers with the 2 inset screws that connects the motor to the gearbox.
This model connects to the other side of the motor and uses the 4 bolt holes to connect to the motor and to the gearbox.
My motor came with 4 countersunk bolts which I used to attach it.

I've printed it in TPU.
6-10 borders
100% infill

I don't know about the longevity yet.