Amplifier board size: 7.1x4.3CM Fixed hole distance: 6.6x3.8CM Bluetooth 5.0, support serial port renaming, support one-key pairing, support AUX inserting to without interruption, power on, the default volume is maximum TX, RX, GND: TTL serial port configuration 9600, N, 8, 1 At 16V4A, the maximum output power is 30W At 12V4A, the maximum output power is 20W 8-22V power supply, with reverse polarity protection, support notebook power adapter power supply Boards and devices, excellent workmanship, sufficient materials, and reliable quality M+ and M- are the positive and negative of the microphone head The appearance and color of different batches , which does not affect the use TYPE:Bluetooth 5.0 Amplifier Board Style: support call function color:Green Material:PCB Package Contents: 1 x Module 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.