INCONEL alloys 625 and 625LCF plus the INCOLOY alloy 800 series of alloys are materials of choice for metallic bellows expansion joints throughout the refinery industry. Their selection is based on proven performance, strength and fatigue properties, stability and corrosion resistance in a host of aggressive environments. Advances in bellows design and manufacture, a better understanding of the effect of refinery operating conditions and improvements in alloy properties based on mill refinements have evolved to the point that refinery engineers now face a myriad of choices in specifying metallic bellows expansion joints. This paper describes the merits of some of these options by reviewing the advances in mill processing and composition of these alloys; by describing some of the options in bellows manufacture and, in particular; by describing the role and effect of post fabrication heat treatment in terms of microstructure and actual bellows fatigue data. Material selection based on corrosion experience in hydrotreating, hydrocracking and catalytic cracking type environments is also reviewed.