Set column width by centimeters or millimeters

Dear all!
Please show me how to set column width by centimeters or millimeters.
Ex:
.Column(3).Width = 86;
But I do not know 86 using what unit type?
Thanks!

The only entry point named is .Column(3).Width; inspect its API definition and existing documentation to identify the current width unit and whether metric units are supported. Reproduce the behavior with a small ClosedXML example, then clarify whether the requested outcome is documentation or support for centimeter and millimeter conversion.

Written by the indexing model from the issue text.