Radius evolution of a 9.40 M_⊙ RSG during rapid envelope removal to mimic a CE in 1D. The envelope of the RSG is artificially ejected on a dynamical timescale until the remnant core mass reaches different values of 2.97, 2.85, 2.80 and 2.75 M_⊙. The evolution of the corresponding surface radius is indicated by the solid lines in different colours as a function of time since the onset of the 1D-CE. The end points of the radius evolution are marked by circles with corresponding edge colours. For comparison, the black dot-dashed line indicates the RSG radius at the onset of the 1D-CE simulation. The Roche lobe radius of the RSG remnant after the CE with a BH and a NS companion is represented by the rectangles filled with transparent and dark colours, respectively.