Top-left: velocity of the CSM versus the CSM mass retrieved from the CSI modeling of 24 SNe Ibn of the MOSFiT sample. The velocity of the CSM is estimated either from the minimum of the absorption component of the P-Cygni profile (red circles) or the FWHM of the emission component (olive squares) of He I λ5876 Å line. Top-right: similar to to the top-left panel, showing the velocity of the CSM versus the CSM density. Bottom-left: broadest velocity component of the He I λ5876 Å line through the entire spectroscopic evolution versus the sum of the CSM and ejecta masses from MOSFiT CSI modeling. Bottom-right: similar to the bottom-left panel, showing the broadest velocity component of He I λ5876 Å line versus the ejecta velocity from MOSFiT CSI modeling.