The 416 buffer seal has a bronze filled PTFE ring with a pre-loaded lip energised by an O-Ring. The seal is designed to protect the primary rod seal from pressure spikes in the cylinder. It has a self relieving design in order to prevent excessive pressure build up in the cavity between the buffer seal and the rod seal.
The special PTFE ring has the low frictional properties normally associated with this material but is strenthened by additives to reduce creep. It has a low breakout friction so stick slip is eliminated.