Comparison of terminal velocities υ_∞ determined by spectral fitting (this work) to those determined by locating υ_black (Crowther et al. 2016). Circles indicate sources for which Crowther et al. (2016) estimated υ_∞ based on υ_black, solid triangles indicate sources for which they used 0.8υ_edge. Grey symbols indicate sources for which we could not obtained a good fit to the C iv λλ1548–1551 profile. The thick red dashed line shows where the two methods agree, while the blue solid line shows a linear fit through the data. See also Fig. 22.