The scarf rings come in different sizes, some of mine look like actual rings that even fit my finger while another is that oval like shape with two holes...go on Hermes.com and you see what they have. Hope this helps.
I have a few scarf rings. One horn ring that I bought to use for shawls. It also works with silks. I finally found two of my grail rings -- a square one (I found on the QM2 Hermes Boutique in December,) and a long wooden/mother of pearl loop. It's about 3 inches or so. My SA taught me how to use it on a regular 90 as well as a GM. It was really a find at an H sale. The best thing was DH was able to remove the "S" mark from it without marring the wood, so it is reversible.