Initial (top rows) and final (bottom rows) period distribution for the WD+MS binaries in models C1, C2, C3, C4 and C5 (α = 1.0 and fully conservative mass transfer, with different prescriptions for q_crit, following Table 2 – colored histograms). The colors indicate the type of interaction the system undergoes to end up as a WD+MS binary. The numbers in the bottom rows indicate the number of systems in the final distribution according to type of interaction. The dark gray line in the top plots shows the normalized period distribution for the entire simulated population (following Raghavan et al. 2010), including systems that do not end up as WD+MS binaries, but as double WDs, MS+MS binaries, mergers, and WD binaries with post-MS stars. All models are initialized with the same period distribution. The final period distribution of the WD+MS binaries are quite different between the models, indicating a strong dependence on mass transfer stability assumptions.