I am thinking of installing two Nicro 3" day/night plus solar powered vents, one for intake, the other for exhaust. Any comments on these or other brands? Did they come with trim rings and other items needed for installation (I do know I will need a sealant)? Do they have to be closed when it rains? It seems they all have dampers, closing them seems to defy the point of trying to ventilate while I am not with the boat.