NOS Mopar battery tray protector.  If your car is 100% factory original (untouched) there is about a 99% chance you will have one of these under your battery.  Why did Chrysler use these?  To help keep any battery acid (or any other harmful/caustic liquids such as brake fluid, etc..) from leaking down onto your engine bay parts located below the battery.  (such as your car's heater control valve, engine wiring, intercooler hoses, etc..).  I can't tell you how many cars we have restored that needed one of these.  Because they didn't have one, the parts I just mentioned were eaten by battery acid.  If you don't currently have one, you need one. Available until supplies run out.