This specification covers a virgin, unfilled polytetrafluoroethylene (PTFE) in the form of extruded and sintered rods, tubes, and profiles. These products have been used typically for parts, such as insulators and bushings requiring chemical inertness up to 500 °F (260 °C), but usage is not limited to such applications. For such applications such as bearing, seals, and back-up rings that do not require dielectric properties and radiographic inspection it is recommended to us AMS 3678/1 Grade B.