<?xml version="1.0" encoding="utf-8"?>
<!-- http://blog.flexexamples.com/2008/10/04/setting-the-tab-width-on-a-tabbar-control-in-flex/ -->
<mx:Application name="TabBar_tabWidth_test"
        xmlns:mx="http://www.adobe.com/2006/mxml"
        layout="vertical"
        verticalAlign="middle"
        backgroundColor="white">

    <mx:Style>
        TabBar {
            tabWidth: 120;
        }
    </mx:Style>

    <mx:Array id="arr">
        <mx:Object label="Red" />
        <mx:Object label="Orange" />
        <mx:Object label="Yellow" />
        <mx:Object label="Green" />
        <mx:Object label="Blue" />
    </mx:Array>

    <mx:TabBar id="tabBar"
            dataProvider="{arr}" />

</mx:Application>