Crutchfield Customer Review (What's this?)
This filter is the best if you have alternator whine. When using the headphone jack and charging at the same time, this eliminated that annoying WEEEEEEEEEE. For the cost it is worth trying before rewiring your system like I did. Give it a try and save yourself the headaches I did before you rewire.
Pros: Small enough it fits anywhere
Cons: But longer wiring of unit would be nice so I could hide it.