HPHT seals combine HNBR, FKM Type 3, or FFKM with specialized carbon black and silica fillers to resist RGD. The key is a fine balance of cross-link density and plasticizer content. Too soft = splitting; too hard = extrusion. Modern compounds achieve 70–90 Shore A while passing 100 % RGD survival at 204°C and 20,000 psi per TOTAL GS EP PVV 142 Annex C https://globalsealstech.com/product/rgd-rapid-gas-decompression-o-rings/