The Bluetooth standard has evolved, and new versions that improve the streaming protocol have been released. For example, Bluetooth 4.0 uses less power than earlier versions. Generally, new versions improve one of two things: they increase the amount of data that can be transferred, or they increase the distance at which a device can send and receive data. The music portions of the Bluetooth standard haven’t changed in versions 4.1 and 4.2, but some devices running ancient versions are still out there. For best audio results, make sure the Bluetooth car kit you buy supports Bluetooth’s Advanced Audio Distribution Profile (A2DP) at a minimum.