Just bought some slip on exhaust. I started to take the stock exhaust off. And the 1 inch ring in the stock exhaust won't come out. Does anyone know what these are called?

Let me take a guess. Are they exhaust gaskets? I would find out if you need to leave those in with your zaust. You might have gotten lucky that they stuck in place. I had one stick to the mid pipe and the other stick inside the collector. No issue here though. I was removing all for a full system.

The exhaust donut is usually soft, gets brittle with age, sometimes they stick to one pipe or the other. Use a small flat blade screwdriver and gently work around the edges. If you take your time and are careful it should come out I one piece.