The frames of Xezo titanium sunglasses are made of pure, 100% titanium (a material with the highest strength-to-weight ratio of any metal), and are nickel-free and non-allergic. The lenses are made of polycarbonate material which is impact-resistant, scratch-resistant and polarized for most models. They offer above 99% protection against the harmful effects of ultraviolet (UV) radiation. Xezo titanium frames are produced in limited-editions for most of our models, and a few of those selected models are individually numbered. The sun lenses in the Xezo titanium frames can be replaced with prescription lenses by an optician, should this ever be required