Ferrite Coils are magnets that surround the wire and reduce the
interference of radio frequencies coming from the LED light. It is an issue
with after-market and more sensitive radios. In electronics, a ferrite core is
a type of magnetic core made of ferrite on which the windings of electric
transformers and other wound components such as inductors are formed.
It is used for its properties of high magnetic permeability coupled with low
electrical conductivity (which helps prevent eddy currents).

Dimensions:    1-1/4" x  5/8" X  1/2"

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