The rated working voltage is 2.5V - 5V, and the limit working voltage is 5.5V. Ultra Mini Size: 21 x 18 x 3.4mm(L x W x H). Various digital can be easily placed in a small space for efficient amplification; double-sided wiring can properly solve the wiring caused by potential balance and crosstalk between channels Two-channel stereo, 5V power supply can output 3W+3W power, can directly drive 4, 8 small speakers, the output power is , the energy is sufficient, and the sound is good. noise suppression, no audio input with ears to speakers, no noise can be heard; unique D digital powerless board with LC filter can be powered directly from the computer's USB. For any DIY design requires a miniature audio amplifier, especially battery powered portable and mobile applications. Colour:green Material:ABS Package Contents: 10 x Digital Power Amplifier Board Only the above package content, other are not included. Note: Light and different displays may cause the color of the item in the a little different from the real thing. The measurement allowed error is +/- 1-3cm.