Piston Seals or Glyde Rings are used in hydraulic cylinders for fluid sealing. They are internal to the cylinder head and seal against the cylinder bore, preventing fluid from flowing across the cylinder head. This allows pressure build up on one side of the piston, making the cylinder extend or retract. â?? Seal Materials (PTFE Grades): BR40, BR40M5, BR55M5, GL5M5, GL15M5. Temperature Range: -50�°C + 200�°C (Depend upon O ring material) Operating Pressure: Up to 800 bar (80Mpa) O Ring material: Nitrile Rubber, Viton. Seal Profile Size Range: We manufacture PISTON Seals for the following range of cylinder bore diameter - 8mm to 700 mm