It is a felt liner that wipes the window clean of debris on the inside. From the factory, Ford just put a piece of plastic so it ends up scratching the tint and sometimes even the windows.

Here's install instructions:

https://mustangforums.com/m_3059554/tm.htm

 

Thanks.

 

I went to a craft store like Michaels and bought some self-adhesive felt...it has been on my stang for almost two years now..thru rain/cold/heat and still going strong. Just as an alternative...