I love my Tifosi Slips. They fit me well, come with four lenses, and are not terribly expensive. When I had a bad fall in August and they broke, I emailed Tifosi and they sent me a replacement pair. Can't get much better than that! I think that the optics are good and the lenses wrap around a little bit on the sides so that I have peripheral sun and wind protection. Some people have had trouble with the lenses breaking at the narrow part in the center but I have been careful and never had a problem. I now have one pair in my car as well as my cycling pair!

http://www.tifosioptics.com/interchangeable/slip.html