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 products 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 4Ω, 8Ω small speakers, the output power is large, the energy is sufficient, and the sound quality is good. Excellent noise suppression, no audio input with ears close to speakers, no noise can be heard; unique Class D digital powerless board with LC filter can be powered directly from the computer's USB. For any DIY design that 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 products are not included. Note: Light shooting 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. Product Notes: Please allow a little manual errors.Due to the lighting of the photos and the difference of monitors, the pictures may not reflect the actual color of the real item. Please confirm acceptance before ordering. About Shipping: Please ensure your shipping informations are correct to avoid delivery issues. All orders are shipped within 3 days after payment. Delivery usually takes 8–12 days, The specific delivery time is depend on circumstances. If you have any questions during your purchase, feel free to contact us. We will respond you within 24 hours.