Abstract: A seal comprises a sandwich of a soft, low modulus resinous layer between two outer layers of harder, high modulus resinous material to provide an effectve high pressure seal at both low and high temperatures. The seal can be used in well head service, e.g., in a blowout preventer or stuffing box seal, in oil wells, geothermal wells of hydraulic mining pipes. The high modulus material is preferably a polybenzimidazole containing 5 to 50 wt. % short fibers. The low modulus material is preferably a thermoplastic fluorinated hydrocarbon polymer or a fluorinated synthetic elastomer containing polybenzimidazole in powder and/or short fiber form and short fibers of glass and/or carbon. For blowout preventer service, the seal can take the form of a T to be fitted with complementary metal retainers to form a cylindrical seal unit having a semicylindrical groove in the seal face to mate with the polish rod or tubing.