The 646 features:

• Threaded chestpiece drum permits the use of five interchangeable chestpiece fittings an adult and pediatric diaphragm, and three bells (11/4", 1", 3/4") - for complete diagnostic capability in most patients
  
  
• All metal parts finished in black chrome for a striking appearance
  
  
• Latex-free double tube configuration
  
  
• Proprietary valve mechanism eliminates acoustic leakage
  
  
• Adjustable binaurals
  
  
• Complete with an accessory pouch containing the bell chestpieces, chestpiece key, 2 spare diaphragms, one pair of mushroom eartips, and one pair of silicon eartips
  
  
• Weighs 8 oz., measures 30”
  
  
• Inspected and packaged in the U.S.A