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. AND PORTABLE :Being so mini and light-weight (2.01x0.59x0.59 IN, 0.99 ), this little gadget does not take much space and can be taken . Audio input: stereo Frequency response: 20HZ-20KHZ Audio Interface: 3.5mm Colour:black :ABS Package Contents: 2 x noise isolator 2 x audio 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 a little different from the real thing. The measurement allowed error is +/- 1-3cm.