Size Guide: Learn how to measure with our visual guide: 1- Take the string and measure from the left or right side of your face as shown in the picture. Measure from the ear to the tip of the nose by stretching the string. 2- After taking the measurement, put the string on a ruler and find out how many cm/inch it is. Still debating? No worries - If the size you purchased does not fit your face, you can return or exchange it free of charge within 30 days. MATERIALS Our products are produced from