Temperature service ratings classify API 6A wellhead seals according to operational temperature ranges designated by letter codes including K, L, P, R, S, T, and U classes. Class K and L cover -75°F to 180°F for standard operations. Class P and R extend to 250°F for moderate temperature wells. Class S and T reach 250°F with lower temperature capability to -75°F for arctic applications... https://globalsealstech.com/product-category/oil-gas-seals/api-6a-wellhead-equipment-seals/