I ended up buying the whole vent from Heartland & then spray painting the flap on the new one & only installed the new flap in the old unit. I felt that was the easiest way to replace it. I had full body paint so that was the simplest. I would do that repair the same way again, I think that was a couple of seasons ago. Be careful with the 2 small plastic pins that goes in the housing that the flap hinges on. They are easily broken, in fact that was why I had to replace my flap-one of the pins had broken off. You shouldn't have any problems with the repair done in this manner. Just take your time. The flap flexes enough to allow the pins to be inserted in the old housing, or at least mine did. Good luck. Mine was on an M-18.