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 (20 684 kPa) for code 09 material and 5000 psi (34 474 kPa) for code 10 material. Material codes are based on AMS3678 material types.