The fourth variant of the Z6 is rather more novel - called the Z6c, this particular Z6 combines both CDMA and GSM network functions into one handset, making it an ideal phone for North American customers who want to use a CDMA device at home, but who also want to travel with the same handset globally. For worldwide customers visiting the US, the Z6c isn't necessary as GSM coverage in North America is improving all the time.