Made from sheet steel and attached to the car body, I can call it a body panel. I have lots of personal recommendations for this part being a perfect fit. It is also zinc plated and pressure tested with good fit for the fuel level sender unit mounting. All around good reports.

Addendum March, 2018:
That didn't take long to change (quality). I installed a new one procured in March, 2018, and it has the filler neck in wrong location. It is mislocated nearly a half inch toward the right rear corner of the car, so the pipe hits hard on the elliptical opening in the boot floor. I got the mounting straps attached okay (just barely), but had to grind the heck out of the inside of the steel seal retaining ring to get the screw holes to line up. Also move the rubber seal over to fit around the new location of the filler neck, and punch a few more screw holes in the seal for new location. Not good. I recon this should be listed as a Faulty Replacement Part until Moss can get better parts.


Addendum September 2021:
Moss is still selling the faulty parts with filler neck in wrong location. Earlier Moss part number was 456-800, which was the good part. Current Moss part number is 456-801, which is the bad part coming from a different source. Current response form Moss is, "We recommend using a slightly longer hose for the connector pipe". which may get you connected, but does not solve the fitting problem due to misalignment. The implication is that Moss intends to keep on selling these faulty parts, at least until they might deplete inventory, after which the next batch might be better. Don't hold your breath while waiting.

Moss Motors - More information