Prusa i3 Clone X and Y idler upgrade, wobble reduce

This is a replacement for the original X- and Y-idler of the cheap i3 Prusa clone.
Parts needed for Installation:
2 x F623ZZ bearing
1 x M3 screw 20mm
1 x M3 nut (self-locking)

Why upgrade?
First check if the printer bed and the head can sliede smoothly.
If not, have a look at the original pulleys (plastic).
Often the are crooked and that creates a wobble effect at X an Y axis.
Replace the both motor pulleys with precised one of aluminum and replace the 2 idlers.