Question on Coolant Expansion Tank Replacement

Doing a expansion tank replacement on my 07' JCW. I came across the part GROMMET that is used for the bottom insertion of the reservoir, it points out to the front. My question is where does the grommet go into? Is it necessary? And whats the grommet used for? I feel that when I pulled off the reservoir I might of pulled it off a bit to hard and the grommet fell down. I've added a picture for a better view of the question I'm asking?



__________________
This post was auto-generated based upon a question asked on our tech article page here:

[Nick at Pelican Parts]

There is a plastic pin at the bottom of the reservoir, this pin sits in the rubber grommet at the base, in the radiator support.

- Nick