1234 North Avenue Luke Lane
South Bend, IN 360001


T-Lon Solutions

GPI Series Piston Seal

The GPI hydraulic piston seal is a proven reliable seal for both low and high pressure systems. The GPI seal is a double-acting filled T-LON® PTFE compound with an o-ring elastomer energizer designed for reciprocating applications. The filled PTFE seal ring is manufactured with an interference fit with the bore and optimum compression with the o-ring energizer. This offers excellent sealability at low pressures and high pressures when the cylinder experiences ballooning. Since the energizers are standard AS568 o-ring sizes, many elastomer compounds are readily available. The chamfers on the GPI ring aid in assembly and crossing over ports in the cylinder.




  • Low seal drag/friction (Minimize energy loss)
  • No Stick-slip (Smooth Operation)
  • Long seal life from T-LON® filled PTFE compounds
  • Available for cylinders up to 20″ diameter


  • Mobile Hydraulic Cylinders
  • Pneumatic Piston Cylinders
  • Agriculture Equipment
  • Hydraulic Valves and Pumps
  • Filling Machines
  • Testing Machinery

Face Grooves (Optional): For applications of high pressure rise rates, pressure spikes, and rapid change of direction, the seal is apt to experience blow-by. To prevent blow-by and to energize the seal rapidly, face grooves are added to both sides of the seal.

Technical Data:

(1) T-LON® seal compound determines allowable pressure and velocity ranges

Velocity: Up to 12 ft/s

Pressure: Up to 8500 psi (Function of e-gap and T-LON® compound. Max velocity and pressure cannot be used together)
Most Common:

BRONZE FILLED PTFE (“21” or “22”)

  • Highest Extrusion Resistance (Higher bronze content increases extrusion/wear resistance; I.E. larger e-gap allowable)
  • Good sealability


  • Good wear resistance for tubes with rougher surface finish
  • More chemical resistant and used in applications when seal could run dry

(2) Loader compound determines temperature and chemical compatibility

Most common:

NBR SHORE 70 A (“P”)

  • Working Temp. Range -30°F to 230°F (250°F intermittent)
  • Commonly used with greases, aliphatic hydrocarbon mineral and vegetable oils, and various hydraulic fluids


  • Working Temp. Range -50°F to 300°F (400°F steam intermittent)
  • Commonly used with water, steam, water/ silicone/ glycol based fluids, and app’s affected by ozone and weathering.

Download Product PDF

Have questions? Our team is ready to help with anything you need. Feel free to reach out.

Contact T-Lon 888.340.TLON