This specification covers one grade of polytetrafluoroethylene (PTFE) in the form of extruded and sintered rods, tubes, and profiles. These products have been used typically for parts, such as bushings and insulators, requiring chemical inertness up to 500 °F (260 °C) and better mechanical and/or electrical properties than AMS 3656, but usage is not limited to such applications. When improved dimensional stability is required, it is recommended that stress relieved product in accordance with AMS 3659 be specified. For parts such as seals, back-up rings and bearings that do not require dielectric properties and radiographic inspection it is recommended to use AMS 3678/1 Grade B.