Kalrez (Compound 4079) Seals for FS5000 Series Flow Switches. Temperature Range: -1 to 104°C (+30-220F). Kalrez is a carbon black filled product with excellent chemical resistance, good mechanical properties, and outstanding hot air aging properties. Low swell in organic acids, inorganic acids and aldehydes, and has good response to temperature cycling effects. Kalrez is not recommended for use in hot water/steam applications or in contact with certain hot aliphatic amines, ethylene oxide, or propylene oxide. Replaces the standard Viton Seals.