Ok I got a pair of Serengeti sunglasses model 6935 and I like the fit and style but the one problem I have is that they don't get dark enough. I guess I'm just hyper sensitive to sunlight. Does Serengeti make a darker version of the velocity? I see the term espresso but can't find any documentation to explain the different model numbers or what espresso means. I wish there was a store I could goto that sells the different styles so I could try them on. Any info or suggestions would be greatly appreciated.