Back-up Rings are used in conjunction with O-rings in both static and dynamic sealing applications, PTFE Back-up Rings are used to prevent the O-ring from entering the clearance gap, when high pressures are exerted on the O-ring, its soft rubber material can be forced into the clearance gap causing the O-ring to extrude, PTFE Back-up rings keep the O-ring material from flowing into the gap which will prevent premature failure. PTFE Back-up Rings are made in single turn “scarf cut”, Spiral “multi-turn”, and solid “uncut”