Usage Tips: Eliminates buzzing noise caused by ground loops in some car speakers or home stereo systems. No external power supply required; this noise isolator helps achieve clear audio by reducing current noise in certain car speakers or home stereo systems. Compatible with any portable device featuring a 3.5mm jack for use with Car Systems or Home Stereos. Compact and lightweight design saves space and allows for easy portability. Item type: Ground Loop Noise Isolator Interface: 3.5mm Frequency response: 20Hz-20kHz Input: Stereo Size: 59 x 20 x 18mm Material: Plastic Color: Black Package Contents: 2 x Ground Loop Noise Isolators or 4 x Ground Loop Noise Isolators Note: The package includes only the items listed above; other products are not included. Light reflection and differences in display screens may cause slight variations between the color of the item in the photo and the actual product. Measurement may vary by +/- 1-3cm.