This SAE Aerospace Standard (AS) covers scarf-cut polytetrafluoroethylene (PTFE) retainers (backup rings) for use in glands in accordance with AS4716. They are for use in hydraulic and pneumatic system components as anti-extrusion devices in conjunction with O-rings, packings and other elastomeric seals for static and dynamic applications.

Because of the construction of groove dimensions, backup rings specific to rod applications are designated “R” - Rod (Female), backup rings specific to piston applications are designated “P” - Piston (Male). Piston and rod types of virgin pigmented PTFE are also identified by color code which also distinguishes parts to this standard from those made from virgin PTFE to other standards.