The WR-RSG interaction in low resolution, showing density in cgs of the CSM and the velocity field for simulation A1 after 7920 (left panel) and 39 200 years (right panel). At first, the shell clearly shows the development of linear Vishniac instabilities. As the shell moves outward, RT instabilities appear as well, leading to large scale disruption of spherical symmetry. In the right panel, both Vishniac and RT instabilities remain visible.