Great glasses for outdoor activities in varied lighting conditions, mountain biking, motorcycle riding, woodcutting, shooting, etc. Don't understand the review which claims they stay dark. Mine sure change tint from full on dark to clear with only a slight tint. I've owned several photochromic glasses before, both prescription (before lasik surgery) and afterwards and these are superior. They aren't cheap but better than eye injury or an accident caused by wearing dark sunglasses in changing light conditions. Retired Army.