Use this seal rather than the generic ones you buy on amazon or camping world. The reason is, those are constructed in sections and glued together, creating seams in the corners where rain and condensation water from the AC running can penetrate where the seams are. This manufacture cuts theirs from one solid piece of closed cell foam. Here’s the link: Steele Rubber Products RV Roof Mounted A/C, Heat Pump Gasket Kit - Sold and Priced by The Set 70-3905-207
https://www.amazon.com/dp/B07TW7QY16..._LGtdFbN89TF9Y