Dref is polymer-specific coupling whose values for a variety of systems have been reported, and takes pre-averaging due to fast chain modes within a Kuhn segment into consideration. The equation is a measure of the average molecular weight (Mc, in units of mol/kg) of chains in terms of the number of segments (N) between cross-links or other topological constraints. Through the measurement of Dres via a multiple-quantum (MQ) pulse sequence, based on the pulse sequence of Baum and Pines, this approach has been applied for measurement of cross-link density and its distribution in complex materials like polyisoprene/polybutadiene (IR/BR) blends and natural rubber/styrene-butadiene rubber (NR/SBR) blends . Though quantitative, a complete distinction of phase-specific cross-link densities could not be established for these systems as the components were made of similar dipolar couplings. This method has also been extended to elastomer/plastic blends of EPDM and ultralow-density polyethylene (ULDPE) blends, where a spin-spin relaxation time (T2) filter was used to suppress the signals arising from crystalline and crystalline-amorphous interface fractions of the ULDPE phase and to obtain cross-link density of the EPDM phase.