HSG-U-I series are high-torque harmonic drive models, whose torque bearing capacity improved by 30% compared with HS-U-I series. Its flexspline is standard silk-hat shaped structure with compact structure of whole unit. The inner hole of wave generator matches with input shaft directly, which is connected by flat key. It can be Circular Spline fixing and Flexspline outputting, also can be Flexspline fixing and Circular Spline outputting. (Drawings are available upon request)