Creating a reducing duct

[rafilathif]

I just want to Draw a reducing Duct please help me how to add in revit or how to create it please refer my attachment 

Thanks and regards

Rafilathif

[L.Maas]

You want to create or modify a family. Basically this is a large transition duct fitting.

[tuuletin]

The upper duct

1. Use the transition duct fitting. Inspect its properties and find parameters, responsible for its length and displacement from the center line.

or

2. Create a family of a same duct type (whether a fitting or a diffuser) — for example, if this is a some kind of a perforated duct.

The lower duct

1. The same, use the transition duct fitting. Inspect its properties and find parameters, responsible for its length and displacement from the center line.

Note, that the lost length due to these duct transitions or families will not be included into the duct length in a duct schedule.