isn't possible set the width

code example
Code:
	public void onModuleLoad() {

		ToggleToolItem one = new ToggleToolItem("my text");
		one.setWidth("500px");

		ToolBar toolbar = new ToolBar();
		toolbar.add(one);

		ContentPanel panel = new ContentPanel();
		panel.setSize(600, 200);
		panel.setTopComponent(toolbar);

		RootPanel.get().add(panel);
	}