Features: Mini high fidelities headphone amplifier set with USB cable & audioed cord, impedances of 16-300, compact and lightweight, convenient to carry. The two-stage gain switching enhances the signal input to the amplifier circuit to achieve optimal performances of the headphones. 3.5mm AUX input and output can not only output louder sound, but also produce clearer and more realistic stereo sound without distortion. Aluminum alloy housing has strong anti-interference performances and heat resistance, and is durable, providing you with a comfortable handheld experience. Built-in 1000mAh rechargeable battery, capable of working for more than 8 hours and long-lasting standby. Wide compatibility, significantly compatible for various digital devices such as MP3, MP4, mobile phones, laptops, and computers. Specifications: Material: Aluminum Size: Approx. 95x60x16mm/3.74x2.36x0.62inch Impedances: 16-300 Battery: 1000mAh Working Time: about 8hrs Note: Please allow 1-2cm errors due to manual measurement. Please allow for slight color differences due to different display resolution. Package includes: 1x Headphone Amplifier 1x USB Power Cable 1x Audioed Cord