FWZI line widths are significantly higher for O VI than for C III. Both of these facts are consistent with significant impacts from overlying absorption. Inspection of any of Figures 3 - 59 from the Danforth et al. (2002) $\fuse$ ISM atlas of sight lines in the Magellanic Clouds shows that the C III ISM absorption at LMC velocities is typically very saturated and broader than the ISM absorption from O VI. Hence, the portion of the C III SNR emission that is visible from under this ISM absorption is narrower and appears more redshifted. While O VI ISM absorption is also usually present, it is not usually saturated and varies in strength between sight lines. In the SNRs, often a broad base of emission is seen in O VI $\lambda$1032 (for example, SNR 0454-665, Figure 5), and thus a larger FWZI is measured and the central velocity is less shifted than for C III.

Overlying absorption is also obviously present in many cases from inspection of the line profiles themselves. There are some cases where an apparently broad O VI emission line has been partially but not totally absorbed on the blue side by LMC and/or galactic ISM (e.g., 