Part No.:  20BYGH206  Single Shaft Frame Size: NEMA8 Step Angle:  1.8 degree Voltage:  1.92VDC Current:  0.6A/phase Resistance:  3.2 Ohm/phase Inductance:  0.9  mH/phase Holding torque 14Kg-cm Rotor inertia  9  g-cm2 Detent torque: 2 kg-cm Number of wire leads  4 Weight:  0.05KG Length:28mm Front  shaft  diameter: 4mm (1/4'') Front shaft length:  20mm round shaft This model is for Single shaft, with 4mm motor shaft, 20mm front shaft length, round shaft!