Lens width: 2.09 inches
Bifocal Reading Glasses: Regular Clear Lens On Top with Reading At The Bottom Perfect For Outdoor Reading And Distance Viewing. No Longer Will You Need To Carry Multiple Pairs Of Glasses.
Photochromic lenses are based on the intensity of sunlight and ultraviolet lights, darkening the clear lens.(may not change obviously under weak UV lights) .The benefit of photochromic lenses is that in dull, overcast weather or darker surroundings they will clear lenses. But in bright, sunny conditions they will go grey lenses. NOTE:It only changes color in the sun, but does not change under the light. Need to change color after 10-15 seconds in the sun.