Kitchen Sink Stopper, 3-1/2 inch Universal Sink Plug Cover for Garbage Disposal Flange Drain - Stainless Steel Brushed

Q: Why the extra ring? Is it suppose to be installed or saved for future use?

I really don’t know I think it was probably accidentally put in with your shipment it doesn’t come with an extra ring that I am aware of keep it just in case it’s free lol

Q: Is the diameter of this stopper truly 3 1/2 inches? I bought another that said it would fit any 3 1/2 InSinkerator disposal but was too small.

I didn't measure the size of the stopper, mine was to large but made it work.

Q: How has the finish/paint held up over time? My current flange’s paint continues to chip off after only a few months.

It has held up really well. I think it has the same quality as the insinkerator brand name. I have had it in my sink for a couple of months and it still looks brand new. Hopefully that helps!