Rubber Between Assembly and Body?

Hello:

I just replaced my tail lights and I'm super happy that they don't look funny anymore. I'm trying to figure out though, is there a gasket or some kind of a rubber that goes between the light assembly and the body? There seems to be a bit of a gap.

I also have the same concern for the running lights up front. I feel like there should be a rubber piece between the assembly and the body of the truck.

I've tried to find it online and google doesn't return anything useful. Just a bunch of ugly lights people are trying to sell me.

Thank you for your time.