Zero-emission wellhead designs mandate seal systems meeting Shell MESC SPE 77/300 Class A. Only spring-energized PTFE and graphite packing with live loading achieve less than 10 ppm leakage, satisfying the most stringent environmental regulations in California, Norway, and the Netherlands https://globalsealstech.com/product-category/oil-gas-seals/api-6a-wellhead-equipment-seals/