This is the base class for elements that reference MenuMacro objects.

Autodesk.AutoCAD.Customization.ElementBase
    Autodesk.AutoCAD.Customization.VersionableElement
        Autodesk.AutoCAD.Customization.CustomizationElement
        Autodesk.AutoCAD.Customization.IReference
            Autodesk.AutoCAD.Customization.CustomizationReference
                Autodesk.AutoCAD.Customization.ButtonItem
                Autodesk.AutoCAD.Customization.DoubleClickCmd
                Autodesk.AutoCAD.Customization.ImageMenuItem
                Autodesk.AutoCAD.Customization.MenuAccelerator
                Autodesk.AutoCAD.Customization.ScreenMenuItem
                Autodesk.AutoCAD.Customization.TabletMenuItem

Public abstract Class CustomizationReference
Inherits CustomizationElement
Inherits IReference

public abstract class CustomizationReference : CustomizationElement, IReference;