set2: 1 x Mp3 lossless decode board + 10 x Battery Holder Product name: Battery holder; Battery type: 3.7 V 18650 battery (not including batteries) Body size: 7.9 x 2.1 x 2.2 cm (L x W x H) 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 Material: Plastic, Metal/metal Description: This Battery Box Holder for DIY; Spring Clip Design and Easy Internal Battery Can; Not included operation instructions. button to adjust the up and down track switch, volume + -, pause / play, mode switch, Note: "long " 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. colour: blue/ Black Package Contents: 1 x Mp3 lossless decode board 10 x Battery Holder Only the above package content, other products are not included. Note: Light 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.