1.5" inner diameter. I'd like to expand even larger.
I found something at Home Depot (Atron Chain Pliers) but no hard stats given. I may ask them to take a look at it and see if it's something I could use.
https://www.homedepot.ca/en/home/p.chain-pliers.1000655652.html
Or, I'll simply drop by Princess Auto and do a modification to this tool:
https://www.princessauto.com/en/detail/4-in-1-interchangeable-snap-ring-plier-set/A-p8007417e