Metal end cap (MEC) seals provide primary metal-to-metal sealing in API 6A flange connections with elastomeric or thermoplastic energizers. VX/VG style gaskets feature Inconel 718 with PTFE or PEEK inlays for extreme pressure and temperature service. Fire-tested per API 6A Appendix F, they maintain integrity during well emergencies https://globalsealstech.com/product-category/oil-gas-seals/api-6a-wellhead-equipment-seals/