Hello,

It is not recommended to change the size of the Toolbar elements, but it is possible with a CreationFilter. I have created a small sample and if you use the following CreationFilter you will be able to manipulate the width :

  class CreationFilterToolbarWidth : IUIElementCreationFilter
    {
        #region IUIElementCreationFilter Members

        public void AfterCreateChildElements(UIElement parent)
        {
             UltraToolbarsDockAreaUIElement toolbarParent = parent as UltraToolbarsDockAreaUIElement;
             if (toolbarParent != null)
             {

                //looping through the Toolbars to make them with Equal width 
                foreach(ToolbarUIElement uiEL in toolbarParent.ChildElements)  

                 {       

                 //Setting the desired width to each of the Toolbars
                 uiEl.Rect = new Rectangle(uiEl.Rect.X, uiEl.Rect.Y, 500, uiEl.Rect.Height);

                }
             }
        }

        public bool BeforeCreateChildElements(UIElement parent)
        {
            return false;
        }

        #endregion
    }

 And after that you just need to assing an instance of this class to your UltraToolbarsManager component like :

 ultraToolbarsManager1.CreationFilter = new CreationFilterToolbarWidth();

Please let me know if you have any other questions.