FS (floating seat) seals are the most common bidirectional gate valve seat seals. Combining HNBR or Viton energizers with PTFE/PEEK anti-extrusion caps, they provide low-friction, millions-of-cycles service while resisting rapid gas decompression in high-rate gas wells and frac trees worldwide. https://globalsealstech.com/product-category/oil-gas-seals/api-6a-gate-valve-seals/