What is unique about Julbo is that they have some lenses that are extra dark. The Spectron 4 are one such type of lens. If you are looking for an extra dark lens because, you live in an area with very bright sunlight, or because you have sensitive vision, or both, then Julbo Spectron 4 lens are for you. The Dolgan Frames are very light and comfortable and even though they are listed as large, they are not large in the way of the current fashion, with the super sized sunglasses. These frames are fine for both medium and large heads. I own them and I use them for summer time, because I live in an area with very bright summer sun. They are comfortable both on the face and on top of the head when indoors. They don't fog up. I recommend them. They are a great design and a great value. You could pay double from some of the better known and heavily marketed brands and still not get something as nice as these Julbo Dolgan large frames with Spectron 4.