fuel cell question

Today's cars the fuel pump sits in a plastic well, this does 2 things keeps it from sucking air when low and keeps the pump cool being submerged in fuel
yes that is true brain and I agree with that. the reason I posted the question is because I can purchase a cell with or w/out foam for the same application. I wasn't sure why that is. because if its such a big deal to have foam in the fuel cell, then why sell the same fuel cell for the same application w/out foam. I was thinking it was some secret squirrel reason, but I guess it is what it is.