HNBR with 50–60% acrylonitrile content is the workhorse for moderate HPHT applications up to 175°C. Special RGD-resistant grades pass NORSOK with 0000 rating after 10 decompression cycles. Carcass-reinforced HNBR seals are widely used in surface wellheads and Christmas trees where cost versus performance balance is critical https://globalsealstech.com/oil-gas-seals/