Lens Standards - all our sunglasses comply to Australian Standard A.S.1067-2003, which amongst other things, rates lenses according to how dark they are.

Darkness of lenses has nothing to do with UV protection ie even clear lenses can block-out 100% of harmful UV rays.

Lens categories are classified according to how much visible light passes through the lens, expressed in percent. The categories are:

Cat-0: 80% - 100%
Cat-1: 43% - 80%
Cat-2: 18% - 43%
Cat-3: 8% - 18%
Cat-4: 4% - 8%

Cat-4 is not suitable for driving, as the lens is considered to be too dark (during over-cast days or dusk).