This class contains collections of ribbon command buttons

Autodesk.AutoCAD.Customization.ElementBase
    Autodesk.AutoCAD.Customization.VersionableElement
        Autodesk.AutoCAD.Customization.CustomizationElement
            Autodesk.AutoCAD.Customization.RibbonItem
            Autodesk.AutoCAD.Customization.ICustomizationContainer
            Autodesk.AutoCAD.Customization.IImageContainer
                Autodesk.AutoCAD.Customization.RibbonSplitButton

Public Class RibbonSplitButton
Inherits RibbonItem
Inherits IImageContainer
Inherits ICustomizationContainer

public class RibbonSplitButton : RibbonItem, IImageContainer, ICustomizationContainer;