Distributions of orbital periods (P_orb) of circularized orbits at the onset of RLO for the resulting XRBs. The presented systems were identified as initiating RLO at the periastron, and then the separation of the circularized orbit was adjusted following the respective model used. The figure shows the default population with the parameters in Table 2 including circularization at RLO onset at the periastron of the eccentric orbit (solid blue), the population with the circularization at an orbit conserved angular momentum (hatched orange), and the population with circularization at the binary separation of the eccentric orbit (hatched green). The distributions have been weighted with the same factor that normalizes the maximum counts per bin for the default population (with orbits circularized at the periastron shown in solid blue) to 1.