  We study the transverse flow throughout the mass range from $^{20}Ne+^{20}Ne$
to $^{131}Xe+^{131}Xe$ as a function of the impact parameter. We find that at
smaller impact parameters the flow is negative while going through the impact
parameter, transverse flow vanishes at a particular colliding geometry named
GVF. We find that the mass dependence of GVF is insensitive to the equation of
state and momentum dependent interactions whereas it is quite sensitive to the
cross section. So it can act as a useful tool to pin down the nucleon nucleon
cross section.
