Visualisation of the 10⁷ period distributions created by sampling the posteriors from Fig. 5. The light and dark red regions depict 95% and 68% of all distributions. The solid red line is the distribution created with the best-fit values from the posteriors. The blue regions and lines are the same for the WC population from Paper II. The dashed black line is the period distribution for O stars from Sana et al. (2012).