I just got another cobalt and I'm noticing some differences from my 2005 that i had. i just installed a head unit and made my own harness for the stereo but cant remember if the antenna adapter was the same. the one i currently have for the car is the undersized plug to standard antenna adapter. the cobalt has a black plastic sleeve and looks like it is just a thin wire. does anyone have a pn for this style. is it the same as the hhr... thanks everyone