For the depth-specific studies, the separated skin and core of 504 h weathered SBR were compared with an intact sample. As an illustration, MSE-FIDs (only) for the two regions and an and the reference coupling of the monomer units (Dref in Equation ) are different. The distribution widths of these samples are also similar to the values before cross-linking. Thus, it can be deduced that sulfur does not affect the inherent distribution of these constraints within the sample volume, or sulfur characteristically leads to a narrow distribution of cross-links.