ring boring

First, I am newbie, so be gentle! I want to primarily make rings from wood and acrylic. I have a boring head for turning the inside to size. I was also hoping to use it to turn the outside down to size (after roughing close by hand). Depending on the ring size, I can likely use the center...

I decided to try my hand at turning some rings. Naturally, I overlooked the description for the boring head which indicated it was sized as R8. My Nova lathe has an MT2 tailstock. What I can't wrap my head around is the adapter sleeve. The boring head is R8. I need an adapter to size down...