HRD showing possible evolutionary pathways of the primary and secondary components for two different sets of semiconvection mixing efficiencies. The donor tracks with initial masses 12 M_⊙, 14 M_⊙, and 17 M_⊙ are shown as red, green, and blue solid lines. The initial orbital periods are chosen, such that the binary has a period of about P_model = 95 ± 5 d after the mass-transfer event. The surface hydrogen abundances of our models that are consistent with the one measured for 2dFS 2553 is highlighted by a thick black contour and the one measured for 2dFS 163 as a thick gray contour. As the tracks of the secondary models do not differ drastically, only for clarity the track of the mass gainer of the system with the 17 M_⊙ donor is shown as a solid black line. To highlight phases where the stellar models spend most of their time, we overplotted the tracks with dots, equally spaced in time steps of Δt = 30 000 yr. The observed positions of the primary and secondary components of the SMC binaries are shown as yellow stars.