I used a Nema 17 Stepper motor Kysan 42BYGH4803. Remember the pololu driver current limit is default set to 0.7 times the rated current to be save. If it is missing steps turn the drive up with small steps. Needed: Stepper motor: Nema 17 Kysan 42BYGH4803 Bearing: 608ZZ Drive gear: MK7-compatible 5MM shaft Spring: Outside diameter: 10mm, Inside diameter: 8mm, Total coils: 9, Length: 25mm Bolt: 4x M3x20