Sunglasses are categorized based on the amount of light that can pass through the lens. The measurement is called visible light transmission, VLT%, and states the percentage of light that can pass through a lens.
Note that the lens category and darkness of the lenses do not affect the UV protection of the lenses.
All Monokel Eyewear lenses are 100% UV protective and in compliance with European, USA, Australian, and New Zealand standards.
| Category | 0 | 1 | 2 | 3 | 4 |
| Tint | very light | light | moderate | dark | very dark |
| VLT% | 80-100% | 43-80% | 18-43% | 8-18% | 3-8% |
| Driving suitability | day & night | day only | day only | day only | never |