After going through a few headsets that were loose fitting and would feel like they are falling off, the 640E is a perfect fit!  It comes with 3 sized earbuds that will alone hold up the light as air device.  But it also comes with an optional ear hook that makes for a perfect fit.  Functionally it works perfect.  Voice quality is excellent.  Talk time is not as long as the Moto 850 which I had, 5 vs ~9hrs.  And it has the capability to connect to a 2nd bluetooth device and will give a different sounding ring for each.  So now im looking for a desk bluetooth phone to have a home station and a mobile phone connection.