NEMA 17 Stepper motor
A NEMA 17 stepper motor is a stepper motor with a 1.7 x 1.7 inch (43.2 x 43.2 mm) faceplate. The NEMA 17 is larger and generally heavier than for example a NEMA 14, but this also means it has more room to put a higher torque. However, its size is not an indication of its power.
Dimensions
Common Stepper Motor Models
the most commonly used stepper motors in Reprap based 3d printers are the kysan 1124090/42BYGH4803 or the rattm 17HS8401 or Wantai 42BYGHW609
however motors close to NEMA17 size, rated 1.5A to 1.8A or less, 1-4 volts, 3 to 8 mH, 62oz.in (0.44Nm, 4.5kg.cm) or more of torque, 1.8 or 0.9 degrees per step (200/400 steps/rev respectively) can also work.