Specifies the nubbin width, if applicable. This value is required only for facing sketches 1c, 1d, 2 and 6 (FLANGE) equivalents 3, 4, 5, and 9). For sketch 9, this is not a nubbin width but the contact width of the metallic ring.
Typical units (depending on your unit system):
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in
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mm
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cm