Stingers
It's a high end battery terminal. They make models that can accept multiple wire sizes, handy if you're installing external devices like a winch or an amp.
I use IXOS, much cheaper than Stinger since they went out of business years ago but excellent quality. I've run the Stinger stuff before and it is definitely nice stuff if you can score a deal on them. Here's mine:

On eBay:
Pair 2 Terminals Ixos 1 0 4 8 Gauge AWG Battery Terminal with Cover BT450 | eBay

On eBay:
Pair 2 Terminals Ixos 1 0 4 8 Gauge AWG Battery Terminal with Cover BT450 | eBay






- but it works.