product description: support MP3 format, power automatically play, play the status of the red LED update. support U disk (tested over 32G), TF card (tested 16G) playback mode; power default TF card mode, if the TF card does not exist automatically jump to U disk mode, and both devices are installed, you can manually Set the playback mode, please refer to the key operation instructions. button to adjust the up and down track switch, volume + -, pause / play, mode switch, Note: "long press" time about 2S If you use U disk mode, the proposed 5V power supply, some U disk does not support 3.7V power supply. Product specifications Power supply range: 3.7 ~ 5.5V Product Size: 45mm x 36mm Exquisite double board design, large area copper, stable and reliable. Anti-static bag refined packaging, to avoid damage to the way of delivery static electricity. Material: metal colour: blue Package Include: 3 x Mp3 lossless decode board Only the above package content, other products are not included. Note: Light reflection and different displays may cause the color of the item in the picture a little different from the real thing. The measurement allowed error is +/- 1-3cm.