Form: This specification covers a high-temperature-fluid-resistant fluorocarbon rubber in the form of molded rings. Application: Sealing rings primarily for use in contact with air or a variety of fuels@ lubricants@ and hydraulic fluids at temperatures from -15??(+5?? to +260??(+500??. The cross section of such rings is usually not over 0.275 in. (6.98 mm) in diameter or thickness. Standard sizes are as shown in AS 568.