Roche-lobe model of HR 5171 A seen at phase 0.25 compared to an angular scale in milliarcsecond (mas) and a distance scale in astronomical units (AU) compared with some solar system references. The model consists of two stars with a total mass of 39 solar masses separated by 9.6 AU, an orbital period of 1304 d (3.57 yr). The mass ratio q = m_sec/m_prim of 10 was arbitrarily chosen and a circular orbit is assumed. The large scales indicate the farthest extension of the circumstellar environment.