Aluminum matte , stylish and compact design. 3.5mm AUX input and output. Support 160-300ohm impedance, exquisite and portable, easy to carry, can output excellent sound without distortion. High-quality audio, suitable for your mobile phone, MP3, MP4, laptop. Noise reduction function, enhanced dynamic distortion, perfect pure stereo effect, high-definition voice and quality optimization. Product name:Headphone amplifier Input/output port:3.5mm audio port Distortion:0.004% Signal to noise ratio: equal 120dB Load impedance:160-300ohm Frequency response:20Hz-20KHz (3dB) Colour:Black Material:Plastic+Metal Package Contents: 1 * Headphone Amplifier 2 * Cable 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.