U-Seal Packing Standard Materials: 80 Duro NBR (Nitrile, Buna N) 85 Duro FKM (Fluorocarbon) Additional materials may be available. Contact VanSeal for details. Pressures to 1,500 psi High Pressure U-Seal Packing Standard Materials: 80 Duro NBR (Nitrile, Buna N) 85 Duro FKM (Fluorocarbon) Additional materials may be available. Contact VanSeal for details. Pressures to 2,500 psi