3 Pcs NMB 3V -5V DC 2 Phase 4 Wire Micro Stepper Motor Dia 15mm Step Angle 18 Degrees with Metal Gear PM15S-020-SKH4

These are not very powerful, but they are very small and light weight. I soldered phone cord, with connector on the other end, to the motor without any problem. Much easier than the 6mm steppers I bought a year ago that were cheaper at 10 for $5. Out of those ten, 6 of them were ruined trying to solder the motor connections for two of them to use in my project. These have twice the power of the 6mm ones.