Illustration of the initial radial profile of the velocity, density, and temperature for all interaction configurations studied in Sect. 3 and described in Table 1. Three types of inner shell properties are considered, with the unadulterated model he4 and two scaled variants (in density, and in both density and velocity). For the outer shell, we consider an ejecta CSM with two different kinetic energies or a wind CSM with three different mass loss rates.