Evolution of stellar mass (panel a), mass-loss rate (panel b), and wind velocity (panel c) as a function of stellar age (in Myr) during different evolutionary stages of the 20 M_⊙ and 60 M_⊙ stars. The evolutionary stages of the 20 M_⊙ star are shown with red dashed lines and those of the 60 M_⊙ star are shown with blue solid lines. We used these parameters as the initial condition in the hydrodynamic simulation for constructing the corresponding CSM at the pre-supernova stage at 8.64 million years for the 20 M_⊙ star and 3.95 million years for the 60 M_⊙ star. The stellar parameters for the 20 M_⊙ and 60 M_⊙ stars are taken from Ekström et al. (2012); Groh et al. (2014), respectively.