Sensitive: Electronic devices produce certain frequencies that may disturb other electronics that are sensitive to those frequencies. It doesn't matter if it's a household appliance or in an automotive application: Ferrite rings are a common way to curb these disturbances. Hows it work? A ferrite core or bead can be added to an inductor to improve, in two ways, its ability to block unwanted high-frequency noise. First, the ferrite concentrates the magnetic field, increases inductance and therefore reactance, which impedes or filters the noise. Designed: To be used on the output cord of any HID ballast or input wiring on an HID bulb, no matter OEM or aftermarket parts; If your radio is picking up static from your new HID system, these will help.