Celtic knot rolled round to create a ring, making quite a balanced design. Made from a knot with 20 loops and seed 1 using the Knot application.
The diameter of the ring is 17mm on the inside (size 6½/M½), but note that the photos are of the 16mm diameter ring. There are links to some other sizes below, but please send me a message if you'd like me to create a different sized version.
See this Size conversion chart for other size units.