  The high-velocity molecular jet driven by Class 0 protostar IRAS 04166+2706
exhibits a unique saw-tooth velocity pattern. It consists of a series of
well-aligned symmetric knots with similar averaged speeds, whose speeds at
peaks of emission decreases roughly linearly away from the origin. Recent ALMA
observations of knots R6 and B6 reveal kinematic behavior with expansion
velocity increasing linearly from the axis to the edge. This pattern can be
formed by a spherically expanding wind with axial density concentration. In
this picture, the diverging velocity profile naturally possesses an increasing
expansion velocity away from the axis, resulting in a tooth-like feature on the
position-velocity diagram through projection. Such geometric picture predicts a
correspondence between the slopes of the teeth and the outflow inclination
angles, and the same inclination angle of 52$^\circ$ of the IRAS 04166+2706 can
generally explain the whole pattern. Aided by numerical simulations in the
framework of unified wind model by Shang et al. (2006), the observed velocity
pattern can indeed be generated. A proper geometrical distribution of the jet
and wind material is essential to the reconstruction the ejection history of
the system.
