The Kazbek Z87+ safety glasses were designed for long days and demanding conditions. These uncompromising work sunglasses have an unmistakable lifestyle shape, polarized lenses, optional anti-fog technology, and an anti-scratch coating. The Kazbek’s frame is constructed of a nylon composite material that can be tied into a knot. And while we don’t recommend tying yours into a square knot, the rugged flexibility of the frame means you get a comfortable, yet virtually indestructible, pair of Z87+ safety glasses or polarized work sunglasses. A thermoplastic rubber (TPR) nosepiece offers a comfortable, non-slip fit. And the lenses block 99.9% of UVA, UVB, and UVC rays.