I purchased the 12” discs for both the 120 and 240 grit. Initially, I was hesitant to purchase them due to the price, but I think the discs are worth every $ spent. I placed the disc on a wet bat mate and added water frequently to the disc while grinding. I was amazed at how well they work. I was able to smooth the feet of several of my pots and grind off drips. These discs are capable of grinding off much more than you may intend. So, exercise caution and check often.
I've used the cheap Chinese discs for years and they wear out pretty fast. Already this one seems sharper at 120 grit, it almost grinds away too much! Maybe I'd be better with the 240 grit. I'll be ordering more :)