Small designBluetooth FM transmitter for smart phone, hands-free car kit and car battery voltage monitor to ensure safe driving. Music playing mode makes your driving trip full of fun. Three Music Playing ModesListen to music on Bluetooth devices via FM signal or transfer music from MP3 , old speakers, a tablet, etc. to car audio system via AUX cable; it also supports MP3, WMA, WAV, etc. in U disk Music file (32G) Hands-free car kitHigh-performance microphone with noise reduction technology (CVC) allows you to speak clearly. Click a button to answer/reject/redial/end a call. Seamlessly switch between incoming calls and music; supports voice navigation on mobile phones, which makes driving safer. Dual USB interfaceThe car Bluetooth audio transmitter supports charging two devices at the same time. The 2.1A port with lightning bolt icon is used for fast charging. The 1A port with music icon of this bluetooth car kit is also used to read the USB flash driver General CompatibilityBluetooth FM transmitter for car can be used as a hands-free to pair with all the Bluetooth enabled devices. Its AUX input port can also be connected to non-Bluetooth devices via AUX cable, such as MP3, MP4, Walkman CD player or some tablets without Bluetooth function