These are Xscorpion speaker adapter plates.
They allow you to install 6x9 inch speakers into mounting holes that are meant for 5x7 or 6x8 inch speakers.
They're designed for certain Mercury and Plymouth vehicles, but they may fit other cars with the same hole pattern.

They're made of sturdy material, likely plastic or ABS.

They're brand new, in the package.

They're a simple solution if you want to upgrade to larger speakers without cutting up your door panels or rear deck.

They provide the correct screw holes and opening for the 6x9 speaker.
They're easy to install, just screw them in and mount the speaker.
Xscorpion is a known brand for car audio accessories.

They don't have a UPC listed, but they're a standard part.
If you're upgrading your classic car's sound system, these are essential.
They save you from custom fabrication.

They're a direct fit for the application.
Get better sound by fitting bigger speakers.
A solid, practical car audio part.