Instructions for use: 1. Install the TR18650 battery first, pay attention to the positive and negative points! (Battery is purchased by yourself) 2. Two wire link audio speakers, red is positive, black is negative 3. Insert an SD card with song files in the SD card slot or a USB flash drive with song files inserted in the USB interface. 4. Open the open key, it automatically read your SD card or USB flash drive, and start playing songs. If the SD card and USB flash drive are installed at the same time, it read the SD card file and by default. Product Name: Bluetooth Digital Power Amplifier Board Product model: A150 Chip model: PAM8403 Transmission distance: up to 20 meters (no blocking) Supply voltage: 5V (Micro-type input) Number of channels: 2 Maximum power: 5W+5W Product net weight: 42g Product size: 99x64x24mm (without protruding parts) Colour:Black+Green Material:Plastic Tips: The product may be updated constantly ,Due To Different Batches, The Actual Product May Have Slight Differences Or Color Differences, Which Does Not Affect Use Package Contents: 1 * Amplifier Audio 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.