Tubing hanger seals isolate annulus from production bore. Dual or triple redundant FFKM or HNBR seals with PEEK backups are standard. They seal on polished mandrel necks and survive tubing movement, thermal cycling, and pressure reversals throughout the well life https://globalsealstech.com/product-category/oil-gas-seals/api-6a-wellhead-equipment-seals/