Inner diameter: 3" Outer diameter: 3.5" If you are using a heavy weight (winter weight) or heavy nap fabric, a very wide fabric (34"-45"), or have just had difficulty adjusting your sling in the past, you may want our large size rings. The large rings have successfully been used with a gathered shoulder, and are preferred for double-layered slings of nearly any material, as well as thicker wraps that are turned into slings.