Usage Tips:Eliminating Buzzing Noise caused by ground in some car speakers / home stereo systems. No external power supply, this noise isolator can achieve a clear speech/music by eliminating the current noise in some car speakers / home stereo systems. Works with any portable device that has 3.5mm jacks, for your Car System/Home Stereo. Compact and lightweight, it will not take much space and can be easily taken away. Item type: Ground Loop Noise Isolator Interface: 3.5mm Frequency response: 20HZ-20KHZ input: stereo Size: 59 x 20 x 18mm Material: Plastic colour: black Package Contents: 2 x Ground loop noise isolators / 4 x Ground loop noise isolators 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.