Form: This specification covers a virgin@ unfilled polytetrafluoroethylene resin in the form of extruded rods@ tubes@ and shapes. These products have been used typically for parts@ such as seals@ back-up rings@ bearings@ and insulators@ requiring better chemical inertness and dimensional stability up to 260 ??(500 ?? than AMS 3657 and better mechanical and electrical properties than AMS 3656@ but usage is not limited to such applications. Classification: Extrusions are classified as follows: Type 1 Parts@ such as insulating bearings@ bushings@ and mounting posts requiring dielectric strength test (3.2.4). Testing of all other specified properties is required. Type 2 Parts@ such as seals@ back-up rings@ and bearings not requiring dielectric strength test (3.2.4). Unless a specific type is ordered@ Type 1 shall be supplied. Safety - Hazardous Materials: While the materials@ methods@ applications@ and processes described or referenced in this specification may involve the use of hazardous materials@ this specification does not address the hazards which may be involved in such use. It is the sole responsibility of the user to ensure familiarity with the safe and proper use of any hazardous materials and to take necessary precautionary measures to ensure the health and safety of all personnel involved.