Make hands-free calls and play music directly through your car speakers via FM radio. Simply pair with your phone using Bluetooth and connect to your car stereo using FM transmission, instantly! Tune an unused FM frequency (87.5-108MHz) on your car stereo & match it to the X 0604A. It will even mute the music when a call comes in. Call audio is routed through your car speakers and a mic picks up your voice. Dual 3.1A / 1A USB charger in-built.