Assembly: System.Management.Automation (in System.Management.Automation.dll)
These properties are part of the extended type system (ETS) that is used to provide uniform access to base objects by extending PSObject objects. For more information about ETS, see Windows PowerShell Extended Type System (ETS).
For more information about the different properties and how they fit into the ETS system, see PSObject Members.
Although it is possible to derive from this class, there is no established scenario for doing this and any attempt to do so might result in unexpected behavior.