Eliminating Buzzing Noise caused by ground in some car speakers / home stereo .No external power supply, this noise isolator can achieve a clear speech/music by eliminating the current noise in some car speakers / home stereo .Works with any portable device that has 3.5mm jacks, for your /Home Stereo. and lightweight, it will not take much space and can be taken .Item type: Interface: 3.5mmFrequency response: 20HZ-20KHZinput: stereoSize: 59 x 20 x 18mmMaterial: Plasticcolour: blackPackage Contents:4 x Ground loop noise isolatorsOnly 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.