January 2, 2009
      
                  
        
  Author(s)
  Zachary H. Levine,   Ming-Dong  Li,   Anthony P. Reeves,   David F. Yankelevitz,   Joseph J. Chen,   Eliot L. Siegel,   Adele P. Peskin,   Diana N. Zeiger
 
       
            
    
    
        We have characterized a commercially-available polyurethane foam which is marketed for modeling parts in the aircraft, automotive, and related industries. We find that the foam may be suitable for use as a density reference standard in the range below -700