Dynamical term ℱ₁ accounting for the stream cross-section, hydrodynamical effects and the Coriolis force (colored lines) in the calculation of the mass transfer rate. In the bottom panel, the solid gray line represents the term only accounting for the potential geometry for the inner Lagrangian point introduced in Ritter (1988), who also provided a fitting formula (dashed gray line). The thick colored lines show the improved dynamical term for the adiabatic (dot-dashed lines) and isothermal (dashed lines) cases and the Roche potential geometry for the inner (red) and outer (blue) Lagrangian points. The fitting formula (thinner solid lines), closely overlapping with the thicker lines, reproduces the factors within 2.5% across the full range of mass ratio considered.