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Did you mean CIS/2 format?
If you want to export to CIS/2, you need to install a plugin.
You can download this if you are on subscription: https://apps.exchange.autodesk.com/RVT/en/Detail/Index?id=appstore.exchange.autodesk.com%3acis2impor...
And if you use Revit 2015 R2, this one is free: https://apps.exchange.autodesk.com/RVT/en/Detail/Index?id=appstore.exchange.autodesk.com%3aadvancest...