How to Measure Manchu/Cylindrical Rings
Cylindrical Rings need the most accurate size to work.
You must use a caliper (preferably digital caliper) and take the width to the nearest 0.01mm at the widest point of the thumb. If you use a non digital caliper, please check here and learn how to read it:
Measure three times, first a loose measure just lightly touching the skin, and a tight measure pressing against the bone that it even hurts a little. Last, take the length of the proximal phalanges of the thumb.