Back-up Rings (Anti-extrusion Rings)

Product Overview

Back-up rings are used to extend the operating pressure of an O-ring. Either one or two back-up rings are co-located within a groove of increased width, on the low-pressure side of the seal.

When pressure is applied to the sealing system the back-up ring is axially compressed, increasing its radial width to close the extrusion gap. The high shear strength of the back-up ring material is then able to contain the elevated pressures.

Unlike elastomers, which see visco-elastic extrusion, thermoplastic back-up ring materials fail if the maximum shear stress is greater than the shear strength of the material at the operating temperature.

Back-Up Ring

PTFE Back-Up Rings

Back-Up Ring Part no. Format

Back-up Type Designator


Spiral Back-up


Scarf Cut Back-up


Solid Back-up
ISO 3601 Back-up Ring Material
Material Family DesignatorDescription

Virgin Polytetrafluoroethylene (PTFE)


Virgin PEEK

Note: Back-up rings are groove specific, the above part numbering format being only suitable for BS1806 grooves.
Hardware dimensional details are available at:






Spiral Turn Anti-Extrusion Ring

Scarf Cut Anti-Extrusion Ring

Solid Anti-Extrusion Ring Scarf Cut Concaved Anti-Extrusion Ring Solid Concaved Anti-Extrusion Ring
Single Back-Up Ring Spiral Single Back-Up Ring Scarf Cut Single Back-Up ring Solid Single Back-Up Ring Scaft Cut Concaved Single Back-Up Ring Solid Concaved
Double Back-Up Ring Spiral Double Back-Up Ring Scarf Double Back-Up Ring Solid Double Back-Up Ring Scarf Concaved Double Back-Up Ring Solid Concaved Double
Back-Up Ring Type Back-Up Ring Spiral Image Back-Up Ring Scaft Cut Image Back-Up ring Solid Image Back-Up ring Scarf Cut Image Back-Up Ring Solid Image
SpiralScarf CutSolidScarf CutSolid

ISO3601 Back-Up Rings

Back-Up Ring ISO3601 Pt No. Format