The sound of a car system begins at the head unit. If the power carries noise from sources such as the alternator and spark plugs, you will get a horrible experience even with the MOST expensive and highly reviewed products. This is prevented by these filters. I actually use two of these filters. One for the power input for the head unit and one for the clock constant power input to the head unit. These are robustly built units. they are not small but I found ways of hiding them within the dash. Very simple to understand the wiring connections. my system is not the most expensive system you can buy, but my vehicle makes you think you are in a sound stage. Always remember a few other tips. bring the ground of the head unit back to where you ground your amps. Seperate the power from any signal wires as they run back to the amps by at least 2 feet until they come to the amp. Make sure the antenna securely seats firmly into the head unit. ENJOY!

Airplane had a noise problem in my airplane,the intercom picked up electronic noise from my alternator and distorted the passanger so bad it was impossible to understand, it made taking instruction impossible. I installed this inline right after the alternator and problem solved

I installed this and it has noticeably reduces the alternator whine I was getting in my car stereo.

Easy to install, alternator noise was driving me crazy! 10 min install and it is all gone. I tried all the tricks I even ran a new ground from radio to battery. This item is amazing, I will be installing one with every radio i put in from now on!

This product works perfect for my cb radio it had a alt noise now it dont. Perfect.

I prefer this type of a noise filter and they work well.

A great filter. I used it to clean up the power for the speedometer on my 1934 ford street rod.