Plumbing supplies are such a mystery! You will need the large, heavy mounting ring if you are installing a vessel sink that has a rounded bottom. The ring prevents the sink from rolling around on the countertop! I had my sink installed slightly inset into the granite, so didn't need the mounting ring, but this is a nice set, beautiful heavy quality. You will not be disappointed!
The drain & ring are great. Both are great quality and value. Would recommend checking depth of counter, etc before ordering. We can't use the ring (which would look very nice under our vessel) because our granite was 3cm. We will look for an extension for the drain to see if we can make it work. All in all both products are an excellent buy and look great.