The "E" stands for Excluded.  If you were to convert Revit Duct/Pipe to fabrication parts any item with a "E" would not be used during the conversion.  

Nathan Chapman
Production Manager at General Heating and Air Conditioning

Revit Architecture Certified Professional
Revit MEP Mechanical Certified Professional
Revit MEP Electrical Certified Professional
DynaFabrication Package Author

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