Working Principle: 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 . Compatible Models: Works with any portable device that has 3.5mm audio jacks, for your car , home stereo, when grounding issues persist. Also used with a bluetooth receiver, bluetooth hands-free car kit in your car , home stereo. Specifications: Audio input: stereo Frequency response: 20HZ-20KHZ Audio Interface: 3.5mm Material:plastic Color:Black Package Contents: 1 x noise filter 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 a little different from the real thing. The measurement allowed error is +/- 1-3cm.