Heater seal?

[wpavlis]

My original heater was filled with such a large mouse nest it is hard to use it as a reference. I the picture below, is there supposed to be some kind of seal around the heater core where the hose connections leave the box? I don't think a lot of air would get out that way but it seems like there should be something.

[In The Ten Ring]

Mine came that way. Grump Old Man may be able to help you.