Two seperate normalised spectral observations of the C iv λλ 1548, 1551 wind lines of SSN 18, normalised and compared to various models. The observations are shown by the black lines. Red lines are models. Top panel: high resolution E140M observations of SSN 18 (obtained on 28-09-2000) compared to a model with , convolved to the same resolution as the model in the lower panel. Lower panel: low resolution G140L spectrum of the same target (obtained on 30-12-2018) compared to a model with .