Roctee 12 Pack snap-on ferrite cores are superb at reducing high frequency interference caused by home appliances and electronics. These Noise Filter can improve the electromagnetic field around the solenoid, thus avoiding outside interference.Just clip it on and you will get clearer signal and faster data transmission. Feature? -Material: Ni-Zn ferrite Plastic -Color: Black -Mini shape and removable. -Improve the signal quality and shield radiation. Specification: 3cm*1.6cm*1.6cm / 1.2*0.6*0.6 inch (outer dimension). 7mm / 2.7 inch (inner diameter). Application: Car DVR, headset cable, loudspeaker cable, mouse cable, keyboard cable, USB cable video cable,audio cable,data cable, etc. Package Included: 12 x Noise Suppressor Cable Clip for 7mm Cable Note: -Please install them in place near the interference source.(Near the import and export of shielding case as much as possible.)If a cable has equipment that needs to be protected on both sides, install one at each end. -In order to suppress electromagnetic radiation more effectively, the cable can be repeatedly twined around twice. -Depending upon circumstances, identifying and troubleshooting both of affected and offending devices are necessary for successful installation. **As A Reliable Seller** Roctee Team is dedicated to offering our valued customers a great and professional services - Timely Email Reply, Helpful Solutions, Refunds & Returns. Any questions you have, please don't hesitate to tell us.If you have any good suggestions, please let us know.