In previous versions, the sizing tables for rectangular and circular ducts which the program used to design these elements, were defined in the “Design options for ducts” menu (General settings > Options > General options). As of the 2018.i version, these tables are defined in the material libraries of the ducts (General options > Libraries > Material types for ducts > edit or add a material).
This way, the sizing tables can differ depending on the material that is used.
