FRAME SIZING GUIDE
Frame sizes relate to 3 measurements in millimetres (mm):
Diameter of lens
The width of the lens (mm), measured from the bridge.
Width of bridge
The gap above your nose, between the lenses.
Length of side
The length from the lenses to the end of the arm. Usually one of three standards – 135, 140 or 145mm. The side should be long enough to sit comfortably over your ears.
Sizes appear as a series of numbers.
For instance, 54-17/145 would relate to: 54 (diameter of lens), 17 (width of bridge) and 145 (length of side).