For giants (left) and dwarfs (right) the surface gravity log g varies with the effective temperature as shown in Table 1 (black squares), while all the parameter space of MARCS is explored regarding the microturbulence and the mass. Other colours (red, blue, and green squares) correspond to different metallicities. The bottom panels show the absolute value of the difference in the expected angular diameter between a given SBCR and the reference value (solid black line).