This is a Brentronics, Inc Battery Terminal Adapter J-6357A/P thing. I found a few dozen more. These are new They come sealed in bags but for shipping I take them out of the bag and just stick the shipping label on the box itself.
Shipping price is for the lower 48 only I will adjust it if you are in Alaska Hawaii or PR
I have been selling these for years. No idea how the guy selling these for around $100 shipped keeps selling them for that much.
No returns or exchanges.