BT21 Car Bluetooth FM Transmitter MP3 Player Wireless FM Transmitter Quick Charger 1.Dual USB ports allow you to charge two devices simultaneously. The fast charge outlet offers you a fast and efficient charging experience. 2.The smart Bluetooth 5.0 lets you play wirelessly. And it offers a stable and smooth connection. 3.Support hands-free calls, safe driving. With the buttons on the Bluetooth FM transmitter, you can easily control the call mode, music, volume, frequency and playback. 4.Lossless audio decoding technology brings you music enjoyment with nice and pleasant sound quality, compatible with a variety of music playback 5.Insert U disk or TF card into the expansion slot of the device, the device will automatically recognize and play MP3 WMA music files. 6.Digital display screen provides you with real-time voltage monitoring and voice transmission abnormalities. 7.With built-in smart chip, this car MP3 player has multiple protection to ensure safe use, such as overvoltage protection, overload protection, reverse insertion protection, overheat protection ,. Short circuit protection, etc.