Aluminum matte, stylish and compact design. 3.5mm AUX input and output. Supports 160-300ohm impedance, portable and easy to carry, delivers excellent sound without distortion. High-quality audio performance, compatible with mobile phones, MP3 players, MP4 players, and laptops. Noise reduction function, low dynamic distortion, clear stereo sound, high-definition audio and quality optimization. Product name: Headphone Amplifier Input/output port: 3.5mm audio port Distortion: 0.004% Signal to noise ratio: 120dB Load impedance: 160-300ohm Frequency response: 20Hz-20KHz (3dB) Color: Black Material: Plastic + Metal Package Contents: 1 x Headphone Amplifier 2 x Cable The package includes only the items listed above; other accessories are not included. Note: Due to lighting reflections and differences in display screens, the color of the item may vary slightly from the images shown. Measurement error allowed is +/- 1-3cm.