Even though Thumbsavers can be used on your thumb, pointer finger, or middle finger, we base our sizing measurements on your thumb - we jokingly call this the 'Rule of Thumbs' at the office.
Please use a ruler and measure the width of your thumbs Interphalangeal (IP) Joint - the joint that is in the middle of your thumb (indicated by the red arrows below). If it is less than 5/8 of an inch, you need a small / red. If it is between 5/8 of an inch and 7/8 of an inch, you need a medium / white. If it is from 7/8 of an inch to 1 1/8 of an inch, you need a large / blue.