Useful for transferring files from one to the other when there is no Bluetooth ...
When connected, it also allows charging the battery from the phone via USB to the computer.
(Also used to unlock mobile power;)
Cable length: 1.50m (it leaves room).
Taken that seem solid wire + = right diameter cable designed to last.
Used with a SE W902 (not simlock), a W910i (Orange), and Zylo (Bouygues), it is entirely satisfactory.
By cons, small remark received a gray and not black cable as shown in the photo!