Part No. 20BYGH408Single Shaft Frame Size:  NEMA8 Step Angle:  1.8 degree Voltage:  4.32VDC Current: 0.8A/phase Resistance: 5.4Ohm/phase Inductance:  1.5mH/phase Holding torque:  30Kg-cm Rotor inertia: 3.6  g-cm2 Detent torque: 5� kg-cm Number of wire leads:  4 Weight:  0.2KG Length:40mm Front  shaft diameter: 4mm Front shaft length: 20mm round shaft This model is for Single shaft, with 4mm motor shaft, 20mm front shaft length, round shaft! More Order Quantites, more  discount!