What are you looking for?
Answer: They’re size measurements in millimeters.
Have you ever look at the inside of the arm of your sunglasses and wondered what the three numbers mean? 52-20-135, for example? They’re measurements.
The first number (e.g. 52), is the width of the lenses.
The second number (e.g. 20) is the distance between the lenses.
And the third number (e.g. 135) is the complete length of the temple arm, which includes the portion that goes behind your ear.
Many brands will have additional numbers on them as well. On the inside of the arm of the Persol aviators pictured above, for example, you’ll also find the numbers 649 and 24/86.
In this case, the first number (649) refers to the specific model of the frames, while the second two are color codes for the frame and lens.
Photography by Rob McIver Photo