My research says to use 6mil plastic. I have stumbled on a product to stick it online. It is called Windo-Weld by 3m I ordered part 086010 which is 1/4" thick and can be made narrower by stretching it. It was not in as promised this morning so I'll update once I get it and install the plastic. I suspect that it will solve a lot of the interior moisture problem I have. I have had the door cards and plastic off for a few years. I didn't realize until recently that the moisture draining through the door was being evaporated in the cab when the sun came out and that is why everything is so wet. fingers crossed.