I bought these because my other gas station shades didnt have interchangable lenses :D. The interlocking system is just great. I can easily switch from dark lenses for the day to clear lenses for night shift. The clear lenses that I get from the Forest Service are definitely NOT up to par. If I could say one thing about these shades I dont like is they squeeze my head really hard right next to the ears. And I have a really small head.