eliminating the buzzing noise, caused by ground loops which happens when the audio source and the speaker use the same power source in some car speakers / home stereo systems when using the Bluetooth receiver. The working principle of this noise isolator is to 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 audio jacks, for your Car Audio System/Home Stereo, when grounding issues persist. Also used with a Bluetooth Receiver/Bluetooth Hands-free Car Kit in your Car Audio System/Home Stereo direction limited,just plug one jack as input,The other is output. It can use from both sides Audio input: stereo Frequency response: 20HZ-20KHZ Audio interface: 3.5mm Colour:black Material: ABS Size: 11x7x3cm Package Contents: 1 x Noise reduction line Only the above package content, other products are not included. Note: Light 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.