New Owner - What is this for?

[The Car Stereo Company]

they want you to read the damn manual....... all 700 pages of it. hahahaha

 

[RaptorSteve]

I did read somewhere else on the net when I found these parts in my new truck that the reason they don't install them at the factory is because of corrosion issues if they're left in and not used for a long period of time, or at all. Electrolysis occurs or some such. I don't know how much truth there is behind it. I just leave mine in.