If I have a ToolBarItem set to Overflow.Auto and vertically shrink the screen the item is duplicated both in the Overflow popup and in the visible portion of the toolbar. 

The ToolBarButton is missing the ability to set the "aria-label".

When attempting to just add it directly, I get the following error:

• Missing overflow hamburger functionality. When small devices some item should move to the hamburger overflow.
• Floating items left or right as on kendo ui toolbar.

Unlike the TelerikButtons, ToolbarButtons do not have appearance settings options - for example ThemeColor, FillMode, Size etc.