Acxico 2 pcs Mini 5mm 2-Phase 4-Wire 3V 5V Planetary Gear Stepper Motor Linear Screw Slider

Excellent!

This stepper motor should be 4-wire and it is only 2-wire.

Used a multimeter to figure out the phase pair connections. Very quiet and minimal backlash

Bought to experiment for control of n scale railroad switches

I chatted with the rep on Amazon, their supplier doesn't have/isn't willing to give them datasheets. I don't think this is the seller's fault, but it is unfortuntate. These motors need a stepper motor driver and heat up really hot. No documentation on mechanical, electrical, or how to solder them. About 30% of the 40 I bought are defective. This is ok though considering the price and considering that you get two per package. I'll update this review higher if the supplier provides documentation sheets. :-)