4 Base Curvature - The base curvature corresponds to the curve of the lens. The higher the number, the higher the curve. 4 base styles have a “flatter” look. 6-9 base curves hug closer to the face.
CR-39 - CR-39 has been the tried and true method for eyeglass lenses for years. Why? They're lightweight, far less prone to shattering than glass and scratch resistant.
100% UVA/UVB Protection - These lenses come with 100% protection from the harsh rays of the sun.
These measurements include the height of the lens, the width of the bridge, the width of the lens and the length of the arms measured in millimeters.
For example, a 56-17-45-144 frame:
1) Lens Height - 56mm
2) Bridge Width - 17mm
3) Lens Width - 45mm
4) Arm Length - 144mm