The X-KD’s are just a little bigger than Original KD’s, or about 20% to be more specific. These are the shades for those reaching for the bigger hat size or those who prefer larger lenses. While having all the good features of regular X-KD’s the Day2Nite version features photochromic lenses. On a bright sunny day, these lenses are smoke to afford protection from the sun. On cloudy days, nighttime and early morning they are clear to allow maximum visibility while still offering protection from wind, bugs and debris. The lenses are made from polycarbonate and meet ANSI Z80.3 general purpose UVA/UVB and impact resistance requirements.