These metal panel backings cover the windows on the panels. You're ordering a set of 7 aluminum sheets cut precisely to size so you don't cut your hand when trying to use tin snips. Six of the panel backings are identical and should be used for panels #3-#8. Panel 2 has it's own sheet that has a hole in the large window for the 8 yellow LEDs behind the bronica finder. Panel #1 doesn't have metal backings, and you should use the white plastic backings that come with the hero panel decal kit.
1mm thick 6061 aluminum. Panels have holes drilled to accept bolts for the 'u-clip' heat sinks. These hold the panel backings in place so no need for glue. They also serve as a drill guide for making the holes you need in the black plastic volvo panels.
Set of 7.