Archery thumb ring in different sizes for Asiatic ot Mongolian style of draw.
To add the correct size:
Thickness and width are measured at the thumb joint that gives the diameter of the ring in millimeters. (AXB MM) The 2nd step measure is the most important, choose your size to be the closest of that number. Let's say the 1st step measure is 19 but the 2nd step measure is 24 mm, your ring will be the 21x24 one. X and Y measures show other dimensions of the ring.
In case of the Asiatic draw the thumb draws while the index finger supports. With a thumb ring the archer can draw heavier bows because the string won’t hurt his thumb and the release will be smoother and quicker.