Place a ring that fits you well on the screen to find your size. If the blue line is inside the ring, that's your size.

1. Take a piece of paper – whether from a notebook, kitchen roll, or a Post-it note. It's best to cut it into a narrow strip.
2. Wrap the strip of paper around your finger and mark with a pen the point where the two ends overlap.

3. Place the strip of paper at the bottom of the screen to measure the length.