Back-up ring materials matter in RGD events. Virgin PEEK softens above 300°F, allowing elastomer extrusion during decompression. Filled PEEK (30 % carbon or glass) or polyimide (Vespel® SP-21) maintain modulus >800 ksi at 400°F, preventing seal blowout even when internal blisters form in the elastomer. https://globalsealstech.com/product/rgd-rapid-gas-decompression-o-rings/