There are a number of different types of laser lens for a CO2 laser. First, there is the material the lens is made from, which are typically Zinc Selenide (ZnSe) or Gallium arsenide (GaAs). ZnSe lenses are also split into two variants depending on how the coating is applied. Physical Vapour Deposition (PVD) is the cheaper variant and is good for laser power up to 80 watts. Chemical Vapour Deposition (CVD) is a higher quality product and is good for laser power up to 300 watts. Secondly there is the shape of the lens, most common is the plano-convex lens (flat one side and convex on the other), followed by the Meniscus lens (convex on one side and concave on the other).