Lens Savers® are crystal optics that shield focusing lenses and other optical components of a laser from damage arising from the spatter discharged during laser welding or cutting.  Lens Savers® windows not only extend the life of focusing lenses, but also can prevent catastrophic failures which occur when a lens is pierced and the delicate internal optical components of the laser are contaminated.  For CO2 lasers, the principal optical material used as Lens Savers® windows is synthetic single crystal potassium chloride (KCl).