• Lenses will turn grey with exposure to the sun or UV light, will not turn pitch black.  
• plastic lens
• non-polarized
• Lens width: 50 millimeters
• Reading Glasses that darken when exposed to sunlight. The longer the glasses is exposed the darker it gets.
• Impact resistant with 100% UVA and UVB protection. CE and FDA certified.
• Standard Adult size fitment - Spring hinge design to fit various head. (lens width 50mm, lens height 42mm, frame width 140mm, bridge 16mm)
• Photochromic lenses darken substantially in response to UV light in less than one minute, and continue to darken a little more over the next fifteen minutes. The lenses begin to clear in the absence of UV light, and will be noticeably lighter within two minutes, mostly clear within five minutes, and fully back to their non-exposed state in about fifteen minutes.

CE and FDA certified reading glasses. Photochromic lenses filter 100% UVA as well as UVB. UVB light is more energetic and causes sunburn as well as skin damage including cancers, UVA light causes skincancers but not usually sunburn. UVB is blocked by all glass, UVA light is not blocked by ordinary windows or lenses glass.