This SAE Aerospace Standard (AS) covers solid polytetrafluoroethylene (PTFE) retainers (back-up rings) for use in static glands in accordance with AS5857. They are for use in hydraulic and pneumatic system components as anti-extrusion devices in conjunction with O-rings, packings and other elastomeric seals.

Because of the construction of groove dimensions, back-ups specific to rod applications are designated "R" - Rod (Female), back-ups specific to piston applications are designated "P" - Piston (Male).

Retainers specified herein have been designed for a temperature range of -65 to 275 °F (-54 to 135 °C) and a nominal operating pressure of 3000 psi (20.6 MPa) for code 09 material and 5000 psi (34.3 MPa) for code 10 material. Material codes are based on AMS 3678 material types.