The compression set of the HAF-filled rubber vulcanizate increased by 13% as the MBTS/ATU and TMTD/ATU weight ratios in the cure system were raised progressively to their optimum values. A similar trend was also observed for the silica-filled rubber vulcanizate though the rise in the compression set was somewhere between 4 and 10%. Remarkably, there was no clear correlation between the CLD and compression set of the rubber. This was contrary to our results which showed a clear correlation between the two at least for most of the compounds tested(Tables III and IV). It was also encouraging to see that the increase in the compression set as a function of MBTS/ATU and TMTD/ATU weight ratios in the cure system was similar to the trend we observed. It is worth noting that there was no correlation between MBTS/ATU and TMTD/ATU weight ratios in the cure system and CLD of the rubber