There is provided an objective lens which has positive refractive power and has a single lens element having an incident surface from which the collimated beam enters and an exit surface from which the collimated beam emerges. In order to further optimize the opening movement of the covering during the extension of the rollover protective structure of the convertible, the covering is attached to a bodywork part with the aid of a multi-bar linkage which controls the opening movement of the covering. The warp threads extend transversely to the longitudinal direction of the clothing and have a greater flexural strength than the sewing threads. The flexible vane has a second curvature distinct from the first curvature.