The Nike 4301 is a full rim frame, which is made of Memory Metal. Memory metal can be bent and twisted and still come back to its original shape. Not only does memory metal “remember” its original shape, it is also light weight and durable. This model features a rectangular shape with a single bridge. This product offers our standard high quality, distortion-free SF-6 Schott Glass Radiation-reducing lenses with .75mm lead equivalency.