Ray-Ban

What is the model code:

If you already own a pair of glasses, you will see numbers engraved on the inside of the eyewear temple. Those numbers will tell you the following:

The first one is the Model name, then the Lens width and Bridge width.  There is usually a third number which represents the Temple Length, which is the measurement in millimeters of the 'arms' of the frame. Sometimes there is also a fourth number which is the Lens Height.
Each of these numbers is measured in mm.