Link: http://www.computercareonline.com/product_info.php?products_id=793/part-no=Q1273-60228
Recently the HP website started showing the HP DesignJet Carriage Belt and Tensioner assembly Q1273-60228 for DesignJet Plotter models 4000 4500 and Z6100 has been replaced. HP now shows the HP DesignJet Carriage Belt and Tensioner assembly CQ109-67004 as the replacement part.
Be aware of this.