Dimi is correct. However, I have used a very thin film of Permatex Form-a-gasket on one side of cork gaskets (on the side with the part that is removed from the car) simply for ease of removal the next time around - the cork gasket generally stays attached to the part being removed from the car (due to the bond created with the Permatex). This can be very helpful in places where it's hard to get to the other surface for cleaning off torn gasket material.