1.1 This specification covers wrought carbon steel and alloy steel fittings of seamless and welded construction covered by the latest revision of ASME B16.9, B16.11, MSS-SP-79, MSS-SP-83, MSS-SP-95, and MSS-SP-97. These fittings are for This specification covers wrought carbon steel and alloy steel fittings of seamless and welded construction. These fittings are for use in pressure piping and in pressure vessel fabrication for service at moderate and elevated temperatures. The materia