The Kazbek Z87+ polarized safety glasses were designed for long days and demanding conditions. These work sunglasses have an unmistakable lifestyle shape, polarized lenses 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+ polarized safety glasses. A thermoplastic rubber (TPR) nosepiece offers a comfortable, non-slip fit. And the lenses block 99.9% of UVA, UVB and UVC rays. What more could you ask for in a pair of Z87+ polarized safety sunglasses?