Location of the components of KIC 8553788 (star symbols) within the Mass–Radius diagram among others of oEA systems (dot symbols) and others that belong to both oEA and R CMa systems (square symbols). The diamond symbols denote the detached systems with a δ Scuti primary component that are also members of the R CMa group, while the hexagon symbol shows the only semi-detached R CMa system that does not exhibit pulsations. Filled and open symbols represent the primary and the secondary components, respectively. Theoretical ZAMS and TAMS lines were taken from Girardi et al. (2000).