Stepper motors are different from DC motors in that they have to be pulsed to move in set increments. That means you can't simply hook them up to a power supply to make them go, but they have other advantages, like accurate positioning (1 pulse=1 increment of movement), and lots of low-speed torque (ability to twist things). 
     This 4-wire bipolar stepper has 1.8° per step for smooth motion and a nice holding torque. This NEMA-17 stepper motor produces a whopping 4000g*cm of holding torque at minimum. Compares to the NEMA-17 Bipolar 48mm Stepper Motor, this item has a shorter length and Lower rated voltage and current.