MIL-PRF-900F, PERFORMANCE SPECIFICATION RUBBER GASKET MATERIAL, 45 DUROMETER HARDNESS (30 MAR 1973)., This specification covers rubber gasket material for watertight and airtight closures, in the temperature range of -20 Deg. to 130 Deg. F (-28.9 Deg. to 54.4 Deg. C), and other uses.