I used what was on there already, that putty type stuff. I removed what I could then made an edge around the whole vent. Just got done with my passenger side today and no leaks at all. Try to scrape off excess putty that has dripped on the back of the panel because it can prevent a tight seal.then make a decent edge around the vent and try to feel it squish into place when you re-install it and test it out. If you dont have the putty stuff that came on it then try to get something that squishes to make a tight seal.