[Healeys] Spacer Ring?

[rrengineer at dslextreme.com]

I recently bought an aluminum gas tank for my BN2 restoration from Jorge
Cevera in Chula Vista near San Diego.  He also sells on Ebay.  I got a
much lower price by picking it up directly from Jorge.  The tank is very
nice and my original gas cap fits perfectly.  My question is about the
plastic "spacer ring" that came with the tank.  It was attached to the
tank by the supplied sending unit mounting screws.  It is a white plastic
ring about 1/8th inch thick and looks like it could be some sort of a
spacer between the tank and the sending unit.  Is this thing necessary?
I have mounted the sending unit without it, but was just wondering what
the heck it was for.
Mike MacLean
56 BN2
60 AN5