NEMA23 pully and pinion

[dazp1976]

Hey guys i want to move my stepper motors (3Nm NEMA23 Motors) so they will not stick out so much
like here on the Z axis:



so i opened aliexpress and the amount of options of pullies and timing belts was overwhelming
how do you choose the timing belt and the pully?

Thanks!

1. How big do you want the pulley diameter to be (space limitations or weight).
2. What ratio do you want to have.