Time evolution of the primary star in model M_{1, i} = 13.5 M_⊙, q_i = 0.50, and P_i = 6.3 d from the onset of Case B RLOF (left), during core He burning (center), and until the end of the run (right). Top: Kippenhahn diagram. The outermost boundaries are colored corresponding to the most abundant element just below (see legend on the right), and the colored patches are based on the dominating mixing mechanism (see legend on the left). A dashed red line shows the maximum extent of the convective H-burning core during the MS. Bottom: Mass transfer rate (solid) and wind mass loss rate from the primary (dashed).