Making sunglass and eyeglass measurements easy.

 Typically the first number in a sequence (ie. ##-##-###) is the width of one of the lenses. The second is the distance of the bridge around the nose or between the nose pieces. The third number is the length of the temple also known as the armpiece. Numbers are always in millimeters. If you have a measurement of a current pair or know what you fits you well, don't worry about a small variation in the numbers. Remember millimeters are very small and used for extreme accuracy usually in prescriptions.