Enter the thickness of the small end of the hub. This value is referred to as "g0" in the ASME code. The corrosion allowance will be subtracted from this value. For weld neck flange types, this is the thickness of the shell at the end of the flange. For slip on flange geometries, this is the thickness of the hub at the small end. For flange geometries without hubs, such as a blind flange, this thickness may be entered as zero. See Flange Face Figure.