The side guard was the way that they used to keep the sun out of their eyes when the sun was to the side of their face. It was a goggle sunglass that was worn by pilots and was light-weight and perforated for coolness.
Well, they are cool! Not only fun, but actually functional, you might enjoy these when climbing, fishing, at the beach, or driving.
Six lens colors really give you diversity in your looks. Memorable!