Mill Finish Aluminum Honeycomb Panels are un-coated (un-painted) aluminum honeycomb sandwich panels. It is same structure like normal aluminum honeycomb panels: two layers of aluminum sheets and an aluminum honeycomb core. The only specialty is the surface of aluminum is mill finish, which is without any paints or coating. The reason of making surface to be mill finish aluminum, is in order to make it possible for stone veneer to glue on. The mill finish aluminum honeycomb panels are used as substrate (backing panels) to make stone honeycomb panels.