2001 Ford Focus Radio

I'm going to be doing an aftermarket head unit install on my friends 01 Focus. I heard a rumor that you need an adapter for the stock antenna plug, but I can't find this anywhere. Can anyone shed some light on this for me?

Thanks

Hey there I found an adapter at Best Buy they do not stock it on the shelves you have to ask someone in audio and they will get it from the installation bay.

Mike